Provided by: mysql-client-core-5.7_5.7.33-0ubuntu0.16.04.1_amd64 
NAME
mysql - the MySQL command-line client
SYNOPSIS
mysql [options] db_name
DESCRIPTION
mysql is a simple SQL shell with input line editing capabilities. It supports interactive and
noninteractive use. When used interactively, query results are presented in an ASCII-table format. When
used noninteractively (for example, as a filter), the result is presented in tab-separated format. The
output format can be changed using command options.
If you have problems due to insufficient memory for large result sets, use the --quick option. This
forces mysql to retrieve results from the server a row at a time rather than retrieving the entire result
set and buffering it in memory before displaying it. This is done by returning the result set using the
mysql_use_result() C API function in the client/server library rather than mysql_store_result().
Note
Alternatively, MySQL Shell offers access to the X DevAPI. For details, see MySQL Shell 8.0 (part of
MySQL 8.0)[1].
Using mysql is very easy. Invoke it from the prompt of your command interpreter as follows:
shell> mysql db_name
Or:
shell> mysql --user=user_name --password db_name
Enter password: your_password
Then type an SQL statement, end it with ;, \g, or \G and press Enter.
Typing Control+C interrupts the current statement if there is one, or cancels any partial input line
otherwise.
You can execute SQL statements in a script file (batch file) like this:
shell> mysql db_name < script.sql > output.tab
On Unix, the mysql client logs statements executed interactively to a history file. See the section
called “MYSQL CLIENT LOGGING”.
MYSQL CLIENT OPTIONS
mysql supports the following options, which can be specified on the command line or in the [mysql] and
[client] groups of an option file. For information about option files used by MySQL programs, see
Section 4.2.2.2, “Using Option Files”.
• --help, -? Display a help message and exit.
• --auto-rehash Enable automatic rehashing. This option is on by default, which enables database,
table, and column name completion. Use --disable-auto-rehash to disable rehashing. That causes mysql
to start faster, but you must issue the rehash command or its \# shortcut if you want to use name
completion.
To complete a name, enter the first part and press Tab. If the name is unambiguous, mysql completes
it. Otherwise, you can press Tab again to see the possible names that begin with what you have typed
so far. Completion does not occur if there is no default database.
Note
This feature requires a MySQL client that is compiled with the readline library. Typically, the
readline library is not available on Windows.
• --auto-vertical-output Cause result sets to be displayed vertically if they are too wide for the
current window, and using normal tabular format otherwise. (This applies to statements terminated by
; or \G.)
• --batch, -B Print results using tab as the column separator, with each row on a new line. With this
option, mysql does not use the history file.
Batch mode results in nontabular output format and escaping of special characters. Escaping may be
disabled by using raw mode; see the description for the --raw option.
• --binary-as-hex When this option is given, mysql displays binary data using hexadecimal notation
(0xvalue). This occurs whether the overall output display format is tabular, vertical, HTML, or XML.
--binary-as-hex when enabled affects display of all binary strings, including those returned by
functions such as CHAR() and UNHEX(). The following example demonistrates this using the ASCII code
for A (65 decimal, 41 hexadecimal):
• --binary-as-hex disabled:
mysql> SELECT CHAR(0x41), UNHEX('41');
+------------+-------------+
| CHAR(0x41) | UNHEX('41') |
+------------+-------------+
| A | A |
+------------+-------------+
• --binary-as-hex enabled:
mysql> SELECT CHAR(0x41), UNHEX('41');
+------------------------+--------------------------+
| CHAR(0x41) | UNHEX('41') |
+------------------------+--------------------------+
| 0x41 | 0x41 |
+------------------------+--------------------------+
To write a binary string expression so that it displays as a character string regardless of whether
--binary-as-hex is enabled, use these techniques:
• The CHAR() function has a USING charset clause:
mysql> SELECT CHAR(0x41 USING utf8mb4);
+--------------------------+
| CHAR(0x41 USING utf8mb4) |
+--------------------------+
| A |
+--------------------------+
• More generally, use CONVERT() to convert an expression to a given character set:
mysql> SELECT CONVERT(UNHEX('41') USING utf8mb4);
+------------------------------------+
| CONVERT(UNHEX('41') USING utf8mb4) |
+------------------------------------+
| A |
+------------------------------------+
This option was added in MySQL 5.7.19.
• --binary-mode This option helps when processing mysqlbinlog output that may contain BLOB values. By
default, mysql translates \r\n in statement strings to \n and interprets \0 as the statement
terminator. --binary-mode disables both features. It also disables all mysql commands except charset
and delimiter in noninteractive mode (for input piped to mysql or loaded using the source command).
• --bind-address=ip_address On a computer having multiple network interfaces, use this option to select
which interface to use for connecting to the MySQL server.
• --character-sets-dir=dir_name The directory where character sets are installed. See Section 10.15,
“Character Set Configuration”.
• --column-names Write column names in results.
• --column-type-info Display result set metadata. This information corresponds to the contents of C API
MYSQL_FIELD data structures. See C API Data Structures[2].
• --comments, -c Whether to strip or preserve comments in statements sent to the server. The default is
--skip-comments (strip comments), enable with --comments (preserve comments).
Note
In MySQL 5.7, the mysql client always passes optimizer hints to the server, regardless of whether
this option is given. To ensure that optimizer hints are not stripped if you are using an older
version of the mysql client with a version of the server that understands optimizer hints, invoke
mysql with the --comments option.
Comment stripping is deprecated as of MySQL 5.7.20. You should expect this feature and the
options to control it to be removed in a future MySQL release.
• --compress, -C Compress all information sent between the client and the server if possible. See
Section 4.2.6, “Connection Compression Control”.
• --connect-expired-password Indicate to the server that the client can handle sandbox mode if the
account used to connect has an expired password. This can be useful for noninteractive invocations of
mysql because normally the server disconnects noninteractive clients that attempt to connect using an
account with an expired password. (See Section 6.2.12, “Server Handling of Expired Passwords”.)
• --connect-timeout=value The number of seconds before connection timeout. (Default value is 0.)
• --database=db_name, -D db_name The database to use. This is useful primarily in an option file.
• --debug[=debug_options], -# [debug_options] Write a debugging log. A typical debug_options string is
d:t:o,file_name. The default is d:t:o,/tmp/mysql.trace.
This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by
Oracle are not built using this option.
• --debug-check Print some debugging information when the program exits.
This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by
Oracle are not built using this option.
• --debug-info, -T Print debugging information and memory and CPU usage statistics when the program
exits.
This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by
Oracle are not built using this option.
• --default-auth=plugin A hint about which client-side authentication plugin to use. See
Section 6.2.13, “Pluggable Authentication”.
• --default-character-set=charset_name Use charset_name as the default character set for the client and
connection.
This option can be useful if the operating system uses one character set and the mysql client by
default uses another. In this case, output may be formatted incorrectly. You can usually fix such
issues by using this option to force the client to use the system character set instead.
For more information, see Section 10.4, “Connection Character Sets and Collations”, and
Section 10.15, “Character Set Configuration”.
• --defaults-extra-file=file_name Read this option file after the global option file but (on Unix)
before the user option file. If the file does not exist or is otherwise inaccessible, an error
occurs. file_name is interpreted relative to the current directory if given as a relative path name
rather than a full path name.
For additional information about this and other option-file options, see Section 4.2.2.3, “Command-
Line Options that Affect Option-File Handling”.
• --defaults-file=file_name Use only the given option file. If the file does not exist or is otherwise
inaccessible, an error occurs. file_name is interpreted relative to the current directory if given
as a relative path name rather than a full path name.
Exception: Even with --defaults-file, client programs read .mylogin.cnf.
For additional information about this and other option-file options, see Section 4.2.2.3, “Command-
Line Options that Affect Option-File Handling”.
• --defaults-group-suffix=str Read not only the usual option groups, but also groups with the usual
names and a suffix of str. For example, mysql normally reads the [client] and [mysql] groups. If the
--defaults-group-suffix=_other option is given, mysql also reads the [client_other] and [mysql_other]
groups.
For additional information about this and other option-file options, see Section 4.2.2.3, “Command-
Line Options that Affect Option-File Handling”.
• --delimiter=str Set the statement delimiter. The default is the semicolon character (;).
• --disable-named-commands Disable named commands. Use the \* form only, or use named commands only at
the beginning of a line ending with a semicolon (;). mysql starts with this option enabled by
default. However, even with this option, long-format commands still work from the first line. See the
section called “MYSQL CLIENT COMMANDS”.
• --enable-cleartext-plugin Enable the mysql_clear_password cleartext authentication plugin. (See
Section 6.4.1.6, “Client-Side Cleartext Pluggable Authentication”.)
• --execute=statement, -e statement Execute the statement and quit. The default output format is like
that produced with --batch. See Section 4.2.2.1, “Using Options on the Command Line”, for some
examples. With this option, mysql does not use the history file.
• --force, -f Continue even if an SQL error occurs.
• --get-server-public-key Request from the server the public key required for RSA key pair-based
password exchange. This option applies to clients that authenticate with the caching_sha2_password
authentication plugin. For that plugin, the server does not send the public key unless requested.
This option is ignored for accounts that do not authenticate with that plugin. It is also ignored if
RSA-based password exchange is not used, as is the case when the client connects to the server using
a secure connection.
If --server-public-key-path=file_name is given and specifies a valid public key file, it takes
precedence over --get-server-public-key.
For information about the caching_sha2_password plugin, see Section 6.4.1.4, “Caching SHA-2 Pluggable
Authentication”.
The --get-server-public-key option was added in MySQL 5.7.23.
• --histignore A list of one or more colon-separated patterns specifying statements to ignore for
logging purposes. These patterns are added to the default pattern list ("*IDENTIFIED*:*PASSWORD*").
The value specified for this option affects logging of statements written to the history file, and to
syslog if the --syslog option is given. For more information, see the section called “MYSQL CLIENT
LOGGING”.
• --host=host_name, -h host_name Connect to the MySQL server on the given host.
• --html, -H Produce HTML output.
• --ignore-spaces, -i Ignore spaces after function names. The effect of this is described in the
discussion for the IGNORE_SPACE SQL mode (see Section 5.1.10, “Server SQL Modes”).
• --init-command=str SQL statement to execute after connecting to the server. If auto-reconnect is
enabled, the statement is executed again after reconnection occurs.
• --line-numbers Write line numbers for errors. Disable this with --skip-line-numbers.
• --local-infile[={0|1}] By default, LOCAL capability for LOAD DATA is determined by the default
compiled into the MySQL client library. To enable or disable LOCAL data loading explicitly, use the
--local-infile option. When given with no value, the option enables LOCAL data loading. When given as
--local-infile=0 or --local-infile=1, the option disables or enables LOCAL data loading.
Successful use of LOCAL load operations within mysql also requires that the server permits local
loading; see Section 6.1.6, “Security Considerations for LOAD DATA LOCAL”
• --login-path=name Read options from the named login path in the .mylogin.cnf login path file. A
“login path” is an option group containing options that specify which MySQL server to connect to and
which account to authenticate as. To create or modify a login path file, use the mysql_config_editor
utility. See mysql_config_editor(1).
For additional information about this and other option-file options, see Section 4.2.2.3, “Command-
Line Options that Affect Option-File Handling”.
• --max-allowed-packet=value The maximum size of the buffer for client/server communication. The
default is 16MB, the maximum is 1GB.
• --max-join-size=value The automatic limit for rows in a join when using --safe-updates. (Default
value is 1,000,000.)
• --named-commands, -G Enable named mysql commands. Long-format commands are permitted, not just
short-format commands. For example, quit and \q both are recognized. Use --skip-named-commands to
disable named commands. See the section called “MYSQL CLIENT COMMANDS”.
• --net-buffer-length=value The buffer size for TCP/IP and socket communication. (Default value is
16KB.)
• --no-auto-rehash, -A This has the same effect as --skip-auto-rehash. See the description for
--auto-rehash.
• --no-beep, -b Do not beep when errors occur.
• --no-defaults Do not read any option files. If program startup fails due to reading unknown options
from an option file, --no-defaults can be used to prevent them from being read.
The exception is that the .mylogin.cnf file, if it exists, is read in all cases. This permits
passwords to be specified in a safer way than on the command line even when --no-defaults is used.
(.mylogin.cnf is created by the mysql_config_editor utility. See mysql_config_editor(1).)
For additional information about this and other option-file options, see Section 4.2.2.3, “Command-
Line Options that Affect Option-File Handling”.
• --one-database, -o Ignore statements except those that occur while the default database is the one
named on the command line. This option is rudimentary and should be used with care. Statement
filtering is based only on USE statements.
Initially, mysql executes statements in the input because specifying a database db_name on the
command line is equivalent to inserting USE db_name at the beginning of the input. Then, for each USE
statement encountered, mysql accepts or rejects following statements depending on whether the
database named is the one on the command line. The content of the statements is immaterial.
Suppose that mysql is invoked to process this set of statements:
DELETE FROM db2.t2;
USE db2;
DROP TABLE db1.t1;
CREATE TABLE db1.t1 (i INT);
USE db1;
INSERT INTO t1 (i) VALUES(1);
CREATE TABLE db2.t1 (j INT);
If the command line is mysql --force --one-database db1, mysql handles the input as follows:
• The DELETE statement is executed because the default database is db1, even though the statement
names a table in a different database.
• The DROP TABLE and CREATE TABLE statements are not executed because the default database is not
db1, even though the statements name a table in db1.
• The INSERT and CREATE TABLE statements are executed because the default database is db1, even
though the CREATE TABLE statement names a table in a different database.
• --pager[=command] Use the given command for paging query output. If the command is omitted, the
default pager is the value of your PAGER environment variable. Valid pagers are less, more, cat [>
filename], and so forth. This option works only on Unix and only in interactive mode. To disable
paging, use --skip-pager. the section called “MYSQL CLIENT COMMANDS”, discusses output paging
further.
• --password[=password], -p[password] The password of the MySQL account used for connecting to the
server. The password value is optional. If not given, mysql prompts for one. If given, there must be
no space between --password= or -p and the password following it. If no password option is specified,
the default is to send no password.
Specifying a password on the command line should be considered insecure. To avoid giving the password
on the command line, use an option file. See Section 6.1.2.1, “End-User Guidelines for Password
Security”.
To explicitly specify that there is no password and that mysql should not prompt for one, use the
--skip-password option.
• --pipe, -W On Windows, connect to the server using a named pipe. This option applies only if the
server was started with the named_pipe system variable enabled to support named-pipe connections. In
addition, the user making the connection must be a member of the Windows group specified by the
named_pipe_full_access_group system variable.
• --plugin-dir=dir_name The directory in which to look for plugins. Specify this option if the
--default-auth option is used to specify an authentication plugin but mysql does not find it. See
Section 6.2.13, “Pluggable Authentication”.
• --port=port_num, -P port_num For TCP/IP connections, the port number to use.
• --print-defaults Print the program name and all options that it gets from option files.
For additional information about this and other option-file options, see Section 4.2.2.3, “Command-
Line Options that Affect Option-File Handling”.
• --prompt=format_str Set the prompt to the specified format. The default is mysql>. The special
sequences that the prompt can contain are described in the section called “MYSQL CLIENT COMMANDS”.
• --protocol={TCP|SOCKET|PIPE|MEMORY} The transport protocol to use for connecting to the server. It is
useful when the other connection parameters normally result in use of a protocol other than the one
you want. For details on the permissible values, see Section 4.2.5, “Connection Transport Protocols”.
• --quick, -q Do not cache each query result, print each row as it is received. This may slow down the
server if the output is suspended. With this option, mysql does not use the history file.
• --raw, -r For tabular output, the “boxing” around columns enables one column value to be
distinguished from another. For nontabular output (such as is produced in batch mode or when the
--batch or --silent option is given), special characters are escaped in the output so they can be
identified easily. Newline, tab, NUL, and backslash are written as \n, \t, \0, and \\. The --raw
option disables this character escaping.
The following example demonstrates tabular versus nontabular output and the use of raw mode to
disable escaping:
% mysql
mysql> SELECT CHAR(92);
+----------+
| CHAR(92) |
+----------+
| \ |
+----------+
% mysql -s
mysql> SELECT CHAR(92);
CHAR(92)
\\
% mysql -s -r
mysql> SELECT CHAR(92);
CHAR(92)
\
• --reconnect If the connection to the server is lost, automatically try to reconnect. A single
reconnect attempt is made each time the connection is lost. To suppress reconnection behavior, use
--skip-reconnect.
• --safe-updates, --i-am-a-dummy, -U If this option is enabled, UPDATE and DELETE statements that do
not use a key in the WHERE clause or a LIMIT clause produce an error. In addition, restrictions are
placed on SELECT statements that produce (or are estimated to produce) very large result sets. If you
have set this option in an option file, you can use --skip-safe-updates on the command line to
override it. For more information about this option, see Using Safe-Updates Mode (--safe-updates).
• --secure-auth Do not send passwords to the server in old (pre-4.1) format. This prevents connections
except for servers that use the newer password format.
As of MySQL 5.7.5, this option is deprecated; expect it to be removed in a future MySQL release. It
is always enabled and attempting to disable it (--skip-secure-auth, --secure-auth=0) produces an
error. Before MySQL 5.7.5, this option is enabled by default but can be disabled.
Note
Passwords that use the pre-4.1 hashing method are less secure than passwords that use the native
password hashing method and should be avoided. Pre-4.1 passwords are deprecated and support for
them was removed in MySQL 5.7.5. For account upgrade instructions, see Section 6.4.1.3,
“Migrating Away from Pre-4.1 Password Hashing and the mysql_old_password Plugin”.
• --select-limit=value The automatic limit for SELECT statements when using --safe-updates. (Default
value is 1,000.)
• --server-public-key-path=file_name The path name to a file in PEM format containing a client-side
copy of the public key required by the server for RSA key pair-based password exchange. This option
applies to clients that authenticate with the sha256_password or caching_sha2_password authentication
plugin. This option is ignored for accounts that do not authenticate with one of those plugins. It is
also ignored if RSA-based password exchange is not used, as is the case when the client connects to
the server using a secure connection.
This option is available only if MySQL was built using OpenSSL.
For information about the sha256_password and caching_sha2_password plugins, see Section 6.4.1.5,
“SHA-256 Pluggable Authentication”, and Section 6.4.1.4, “Caching SHA-2 Pluggable Authentication”.
• --shared-memory-base-name=name On Windows, the shared-memory name to use for connections made using
shared memory to a local server. The default value is MYSQL. The shared-memory name is
case-sensitive.
This option applies only if the server was started with the shared_memory system variable enabled to
support shared-memory connections.
• --show-warnings Cause warnings to be shown after each statement if there are any. This option applies
to interactive and batch mode.
• --sigint-ignore Ignore SIGINT signals (typically the result of typing Control+C).
Without this option, typing Control+C interrupts the current statement if there is one, or cancels
any partial input line otherwise.
• --silent, -s Silent mode. Produce less output. This option can be given multiple times to produce
less and less output.
This option results in nontabular output format and escaping of special characters. Escaping may be
disabled by using raw mode; see the description for the --raw option.
• --skip-column-names, -N Do not write column names in results.
• --skip-line-numbers, -L Do not write line numbers for errors. Useful when you want to compare result
files that include error messages.
• --socket=path, -S path For connections to localhost, the Unix socket file to use, or, on Windows, the
name of the named pipe to use.
On Windows, this option applies only if the server was started with the named_pipe system variable
enabled to support named-pipe connections. In addition, the user making the connection must be a
member of the Windows group specified by the named_pipe_full_access_group system variable.
• --ssl* Options that begin with --ssl specify whether to connect to the server using SSL and indicate
where to find SSL keys and certificates. See the section called “Command Options for Encrypted
Connections”.
• --syslog, -j This option causes mysql to send interactive statements to the system logging facility.
On Unix, this is syslog; on Windows, it is the Windows Event Log. The destination where logged
messages appear is system dependent. On Linux, the destination is often the /var/log/messages file.
Here is a sample of output generated on Linux by using --syslog. This output is formatted for
readability; each logged message actually takes a single line.
Mar 7 12:39:25 myhost MysqlClient[20824]:
SYSTEM_USER:'oscar', MYSQL_USER:'my_oscar', CONNECTION_ID:23,
DB_SERVER:'127.0.0.1', DB:'--', QUERY:'USE test;'
Mar 7 12:39:28 myhost MysqlClient[20824]:
SYSTEM_USER:'oscar', MYSQL_USER:'my_oscar', CONNECTION_ID:23,
DB_SERVER:'127.0.0.1', DB:'test', QUERY:'SHOW TABLES;'
For more information, see the section called “MYSQL CLIENT LOGGING”.
• --table, -t Display output in table format. This is the default for interactive use, but can be used
to produce table output in batch mode.
• --tee=file_name Append a copy of output to the given file. This option works only in interactive
mode. the section called “MYSQL CLIENT COMMANDS”, discusses tee files further.
• --tls-version=protocol_list The permissible TLS protocols for encrypted connections. The value is a
list of one or more comma-separated protocol names. The protocols that can be named for this option
depend on the SSL library used to compile MySQL. For details, see Section 6.3.2, “Encrypted
Connection TLS Protocols and Ciphers”.
This option was added in MySQL 5.7.10.
• --unbuffered, -n Flush the buffer after each query.
• --user=user_name, -u user_name The user name of the MySQL account to use for connecting to the
server.
• --verbose, -v Verbose mode. Produce more output about what the program does. This option can be given
multiple times to produce more and more output. (For example, -v -v -v produces table output format
even in batch mode.)
• --version, -V Display version information and exit.
• --vertical, -E Print query output rows vertically (one line per column value). Without this option,
you can specify vertical output for individual statements by terminating them with \G.
• --wait, -w If the connection cannot be established, wait and retry instead of aborting.
• --xml, -X Produce XML output.
<field name="column_name">NULL</field>
The output when --xml is used with mysql matches that of mysqldump --xml. See mysqldump(1), for
details.
The XML output also uses an XML namespace, as shown here:
shell> mysql --xml -uroot -e "SHOW VARIABLES LIKE 'version%'"
<?xml version="1.0"?>
<resultset statement="SHOW VARIABLES LIKE 'version%'" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<row>
<field name="Variable_name">version</field>
<field name="Value">5.0.40-debug</field>
</row>
<row>
<field name="Variable_name">version_comment</field>
<field name="Value">Source distribution</field>
</row>
<row>
<field name="Variable_name">version_compile_machine</field>
<field name="Value">i686</field>
</row>
<row>
<field name="Variable_name">version_compile_os</field>
<field name="Value">suse-linux-gnu</field>
</row>
</resultset>
MYSQL CLIENT COMMANDS
mysql sends each SQL statement that you issue to the server to be executed. There is also a set of
commands that mysql itself interprets. For a list of these commands, type help or \h at the mysql>
prompt:
mysql> help
List of all MySQL commands:
Note that all text commands must be first on line and end with ';'
? (\?) Synonym for `help'.
clear (\c) Clear the current input statement.
connect (\r) Reconnect to the server. Optional arguments are db and host.
delimiter (\d) Set statement delimiter.
edit (\e) Edit command with $EDITOR.
ego (\G) Send command to mysql server, display result vertically.
exit (\q) Exit mysql. Same as quit.
go (\g) Send command to mysql server.
help (\h) Display this help.
nopager (\n) Disable pager, print to stdout.
notee (\t) Don't write into outfile.
pager (\P) Set PAGER [to_pager]. Print the query results via PAGER.
print (\p) Print current command.
prompt (\R) Change your mysql prompt.
quit (\q) Quit mysql.
rehash (\#) Rebuild completion hash.
source (\.) Execute an SQL script file. Takes a file name as an argument.
status (\s) Get status information from the server.
system (\!) Execute a system shell command.
tee (\T) Set outfile [to_outfile]. Append everything into given
outfile.
use (\u) Use another database. Takes database name as argument.
charset (\C) Switch to another charset. Might be needed for processing
binlog with multi-byte charsets.
warnings (\W) Show warnings after every statement.
nowarning (\w) Don't show warnings after every statement.
resetconnection(\x) Clean session context.
For server side help, type 'help contents'
If mysql is invoked with the --binary-mode option, all mysql commands are disabled except charset and
delimiter in noninteractive mode (for input piped to mysql or loaded using the source command).
Each command has both a long and short form. The long form is not case-sensitive; the short form is. The
long form can be followed by an optional semicolon terminator, but the short form should not.
The use of short-form commands within multiple-line /* ... */ comments is not supported. Short-form
commands do work within single-line /*! ... */ version comments, as do /*+ ... */ optimizer-hint
comments, which are stored in object definitions. If there is a concern that optimizer-hint comments may
be stored in object definitions so that dump files when reloaded with mysql would result in execution of
such commands, either invoke mysql with the --binary-mode option or use a reload client other than mysql.
• help [arg], \h [arg], \? [arg], ? [arg]
Display a help message listing the available mysql commands.
If you provide an argument to the help command, mysql uses it as a search string to access
server-side help from the contents of the MySQL Reference Manual. For more information, see the
section called “MYSQL CLIENT SERVER-SIDE HELP”.
• charset charset_name, \C charset_name
Change the default character set and issue a SET NAMES statement. This enables the character set to
remain synchronized on the client and server if mysql is run with auto-reconnect enabled (which is
not recommended), because the specified character set is used for reconnects.
• clear, \c
Clear the current input. Use this if you change your mind about executing the statement that you are
entering.
• connect [db_name [host_name]], \r [db_name [host_name]]
Reconnect to the server. The optional database name and host name arguments may be given to specify
the default database or the host where the server is running. If omitted, the current values are
used.
• delimiter str, \d str
Change the string that mysql interprets as the separator between SQL statements. The default is the
semicolon character (;).
The delimiter string can be specified as an unquoted or quoted argument on the delimiter command
line. Quoting can be done with either single quote ('), double quote ("), or backtick (`) characters.
To include a quote within a quoted string, either quote the string with a different quote character
or escape the quote with a backslash (\) character. Backslash should be avoided outside of quoted
strings because it is the escape character for MySQL. For an unquoted argument, the delimiter is read
up to the first space or end of line. For a quoted argument, the delimiter is read up to the matching
quote on the line.
mysql interprets instances of the delimiter string as a statement delimiter anywhere it occurs,
except within quoted strings. Be careful about defining a delimiter that might occur within other
words. For example, if you define the delimiter as X, it is not possible to use the word INDEX in
statements. mysql interprets this as INDE followed by the delimiter X.
When the delimiter recognized by mysql is set to something other than the default of ;, instances of
that character are sent to the server without interpretation. However, the server itself still
interprets ; as a statement delimiter and processes statements accordingly. This behavior on the
server side comes into play for multiple-statement execution (see C API Multiple Statement Execution
Support[3]), and for parsing the body of stored procedures and functions, triggers, and events (see
Section 22.1, “Defining Stored Programs”).
• edit, \e
Edit the current input statement. mysql checks the values of the EDITOR and VISUAL environment
variables to determine which editor to use. The default editor is vi if neither variable is set.
The edit command works only in Unix.
• ego, \G
Send the current statement to the server to be executed and display the result using vertical format.
• exit, \q
Exit mysql.
• go, \g
Send the current statement to the server to be executed.
• nopager, \n
Disable output paging. See the description for pager.
The nopager command works only in Unix.
• notee, \t
Disable output copying to the tee file. See the description for tee.
• nowarning, \w
Disable display of warnings after each statement.
• pager [command], \P [command]
Enable output paging. By using the --pager option when you invoke mysql, it is possible to browse or
search query results in interactive mode with Unix programs such as less, more, or any other similar
program. If you specify no value for the option, mysql checks the value of the PAGER environment
variable and sets the pager to that. Pager functionality works only in interactive mode.
Output paging can be enabled interactively with the pager command and disabled with nopager. The
command takes an optional argument; if given, the paging program is set to that. With no argument,
the pager is set to the pager that was set on the command line, or stdout if no pager was specified.
Output paging works only in Unix because it uses the popen() function, which does not exist on
Windows. For Windows, the tee option can be used instead to save query output, although it is not as
convenient as pager for browsing output in some situations.
• print, \p
Print the current input statement without executing it.
• prompt [str], \R [str]
Reconfigure the mysql prompt to the given string. The special character sequences that can be used in
the prompt are described later in this section.
If you specify the prompt command with no argument, mysql resets the prompt to the default of mysql>.
• quit, \q
Exit mysql.
• rehash, \#
Rebuild the completion hash that enables database, table, and column name completion while you are
entering statements. (See the description for the --auto-rehash option.)
• resetconnection, \x
Reset the connection to clear the session state.
Resetting a connection has effects similar to mysql_change_user() or an auto-reconnect except that
the connection is not closed and reopened, and re-authentication is not done. See
mysql_change_user()[4], and C API Automatic Reconnection Control[5].
This example shows how resetconnection clears a value maintained in the session state:
mysql> SELECT LAST_INSERT_ID(3);
+-------------------+
| LAST_INSERT_ID(3) |
+-------------------+
| 3 |
+-------------------+
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 3 |
+------------------+
mysql> resetconnection;
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 0 |
+------------------+
• source file_name, \. file_name
Read the named file and executes the statements contained therein. On Windows, specify path name
separators as / or \\.
Quote characters are taken as part of the file name itself. For best results, the name should not
include space characters.
• status, \s
Provide status information about the connection and the server you are using. If you are running with
--safe-updates enabled, status also prints the values for the mysql variables that affect your
queries.
• system command, \! command
Execute the given command using your default command interpreter.
The system command works only in Unix.
• tee [file_name], \T [file_name]
By using the --tee option when you invoke mysql, you can log statements and their output. All the
data displayed on the screen is appended into a given file. This can be very useful for debugging
purposes also. mysql flushes results to the file after each statement, just before it prints its
next prompt. Tee functionality works only in interactive mode.
You can enable this feature interactively with the tee command. Without a parameter, the previous
file is used. The tee file can be disabled with the notee command. Executing tee again re-enables
logging.
• use db_name, \u db_name
Use db_name as the default database.
• warnings, \W
Enable display of warnings after each statement (if there are any).
Here are a few tips about the pager command:
• You can use it to write to a file and the results go only to the file:
mysql> pager cat > /tmp/log.txt
You can also pass any options for the program that you want to use as your pager:
mysql> pager less -n -i -S
• In the preceding example, note the -S option. You may find it very useful for browsing wide query
results. Sometimes a very wide result set is difficult to read on the screen. The -S option to less
can make the result set much more readable because you can scroll it horizontally using the
left-arrow and right-arrow keys. You can also use -S interactively within less to switch the
horizontal-browse mode on and off. For more information, read the less manual page:
shell> man less
• The -F and -X options may be used with less to cause it to exit if output fits on one screen, which
is convenient when no scrolling is necessary:
mysql> pager less -n -i -S -F -X
• You can specify very complex pager commands for handling query output:
mysql> pager cat | tee /dr1/tmp/res.txt \
| tee /dr2/tmp/res2.txt | less -n -i -S
In this example, the command would send query results to two files in two different directories on
two different file systems mounted on /dr1 and /dr2, yet still display the results onscreen using
less.
You can also combine the tee and pager functions. Have a tee file enabled and pager set to less, and you
are able to browse the results using the less program and still have everything appended into a file the
same time. The difference between the Unix tee used with the pager command and the mysql built-in tee
command is that the built-in tee works even if you do not have the Unix tee available. The built-in tee
also logs everything that is printed on the screen, whereas the Unix tee used with pager does not log
quite that much. Additionally, tee file logging can be turned on and off interactively from within mysql.
This is useful when you want to log some queries to a file, but not others.
The prompt command reconfigures the default mysql> prompt. The string for defining the prompt can contain
the following special sequences.
br
.br
.br
72
┌─────────────────────────────────────┬───────────────────────────────────────┐
│Option │ Description │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current connection identifier │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ A counter that increments for each │
│ │ statement you issue │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The full current date │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The default database │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The server host │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current delimiter │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ Minutes of the current time │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ A newline character │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current month in three-letter │
│ │ format (Jan, Feb, ...) │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current month in numeric format │
├─────────────────────────────────────┼───────────────────────────────────────┤
│P │ am/pm │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current TCP/IP port or socket │
│ │ file │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current time, in 24-hour military │
│ │ time (0–23) │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current time, standard 12-hour │
│ │ time (1–12) │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ Semicolon │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ Seconds of the current time │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ A tab character │
├─────────────────────────────────────┼───────────────────────────────────────┤
│U │ │
│ │ Your full user_name@host_name │
│ │ account name │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ Your user name │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The server version │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current day of the week in three- │
│ │ letter format (Mon, Tue, ...) │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ The current year, four digits │
├─────────────────────────────────────┼───────────────────────────────────────┤
│y │ The current year, two digits │
├─────────────────────────────────────┼───────────────────────────────────────┤
│_ │ A space │
├─────────────────────────────────────┼───────────────────────────────────────┤
│\ │ A space (a space follows the │
│ │ backslash) │
├─────────────────────────────────────┼───────────────────────────────────────┤
│´ │ Single quote │
├─────────────────────────────────────┼───────────────────────────────────────┤
│ │ Double quote │
├─────────────────────────────────────┼───────────────────────────────────────┤
│T}:T{ A literal backslash character │ │
├─────────────────────────────────────┼───────────────────────────────────────┤
│\fIx │ │
│ │ x, for any “x” not listed │
│ │ above │
└─────────────────────────────────────┴───────────────────────────────────────┘
You can set the prompt in several ways:
• Use an environment variable. You can set the MYSQL_PS1 environment variable to a prompt string. For
example:
shell> export MYSQL_PS1="(\u@\h) [\d]> "
• Use a command-line option. You can set the --prompt option on the command line to mysql. For
example:
shell> mysql --prompt="(\u@\h) [\d]> "
(user@host) [database]>
• Use an option file. You can set the prompt option in the [mysql] group of any MySQL option file,
such as /etc/my.cnf or the .my.cnf file in your home directory. For example:
[mysql]
prompt=(\\u@\\h) [\\d]>\\_
In this example, note that the backslashes are doubled. If you set the prompt using the prompt option
in an option file, it is advisable to double the backslashes when using the special prompt options.
There is some overlap in the set of permissible prompt options and the set of special escape
sequences that are recognized in option files. (The rules for escape sequences in option files are
listed in Section 4.2.2.2, “Using Option Files”.) The overlap may cause you problems if you use
single backslashes. For example, \s is interpreted as a space rather than as the current seconds
value. The following example shows how to define a prompt within an option file to include the
current time in hh:mm:ss> format:
[mysql]
prompt="\\r:\\m:\\s> "
• Set the prompt interactively. You can change your prompt interactively by using the prompt (or \R)
command. For example:
mysql> prompt (\u@\h) [\d]>\_
PROMPT set to '(\u@\h) [\d]>\_'
(user@host) [database]>
(user@host) [database]> prompt
Returning to default PROMPT of mysql>
mysql>
MYSQL CLIENT LOGGING
The mysql client can do these types of logging for statements executed interactively:
• On Unix, mysql writes the statements to a history file. By default, this file is named .mysql_history
in your home directory. To specify a different file, set the value of the MYSQL_HISTFILE environment
variable.
• On all platforms, if the --syslog option is given, mysql writes the statements to the system logging
facility. On Unix, this is syslog; on Windows, it is the Windows Event Log. The destination where
logged messages appear is system dependent. On Linux, the destination is often the /var/log/messages
file.
The following discussion describes characteristics that apply to all logging types and provides
information specific to each logging type.
• How Logging Occurs
• Controlling the History File
• syslog Logging Characteristics
How Logging Occurs
For each enabled logging destination, statement logging occurs as follows:
• Statements are logged only when executed interactively. Statements are noninteractive, for example,
when read from a file or a pipe. It is also possible to suppress statement logging by using the
--batch or --execute option.
• Statements are ignored and not logged if they match any pattern in the “ignore” list. This list is
described later.
• mysql logs each nonignored, nonempty statement line individually.
• If a nonignored statement spans multiple lines (not including the terminating delimiter), mysql
concatenates the lines to form the complete statement, maps newlines to spaces, and logs the result,
plus a delimiter.
Consequently, an input statement that spans multiple lines can be logged twice. Consider this input:
mysql> SELECT
-> 'Today is'
-> ,
-> CURDATE()
-> ;
In this case, mysql logs the “SELECT”, “'Today is'”, “,”, “CURDATE()”, and “;” lines as it reads them. It
also logs the complete statement, after mapping SELECT\n'Today is'\n,\nCURDATE() to SELECT 'Today is' ,
CURDATE(), plus a delimiter. Thus, these lines appear in logged output:
SELECT
'Today is'
,
CURDATE()
;
SELECT 'Today is' , CURDATE();
mysql ignores for logging purposes statements that match any pattern in the “ignore” list. By default,
the pattern list is "*IDENTIFIED*:*PASSWORD*", to ignore statements that refer to passwords. Pattern
matching is not case-sensitive. Within patterns, two characters are special:
• ? matches any single character.
• * matches any sequence of zero or more characters.
To specify additional patterns, use the --histignore option or set the MYSQL_HISTIGNORE environment
variable. (If both are specified, the option value takes precedence.) The value should be a list of one
or more colon-separated patterns, which are appended to the default pattern list.
Patterns specified on the command line might need to be quoted or escaped to prevent your command
interpreter from treating them specially. For example, to suppress logging for UPDATE and DELETE
statements in addition to statements that refer to passwords, invoke mysql like this:
shell> mysql --histignore="*UPDATE*:*DELETE*"
Controlling the History File
The .mysql_history file should be protected with a restrictive access mode because sensitive information
might be written to it, such as the text of SQL statements that contain passwords. See Section 6.1.2.1,
“End-User Guidelines for Password Security”. Statements in the file are accessible from the mysql client
when the up-arrow key is used to recall the history. See Disabling Interactive History.
If you do not want to maintain a history file, first remove .mysql_history if it exists. Then use either
of the following techniques to prevent it from being created again:
• Set the MYSQL_HISTFILE environment variable to /dev/null. To cause this setting to take effect each
time you log in, put it in one of your shell's startup files.
• Create .mysql_history as a symbolic link to /dev/null; this need be done only once:
shell> ln -s /dev/null $HOME/.mysql_history
syslog Logging Characteristics
If the --syslog option is given, mysql writes interactive statements to the system logging facility.
Message logging has the following characteristics.
Logging occurs at the “information” level. This corresponds to the LOG_INFO priority for syslog on
Unix/Linux syslog capability and to EVENTLOG_INFORMATION_TYPE for the Windows Event Log. Consult your
system documentation for configuration of your logging capability.
Message size is limited to 1024 bytes.
Messages consist of the identifier MysqlClient followed by these values:
• SYSTEM_USER
The operating system user name (login name) or -- if the user is unknown.
• MYSQL_USER
The MySQL user name (specified with the --user option) or -- if the user is unknown.
• CONNECTION_ID:
The client connection identifier. This is the same as the CONNECTION_ID() function value within the
session.
• DB_SERVER
The server host or -- if the host is unknown.
• DB
The default database or -- if no database has been selected.
• QUERY
The text of the logged statement.
Here is a sample of output generated on Linux by using --syslog. This output is formatted for
readability; each logged message actually takes a single line.
Mar 7 12:39:25 myhost MysqlClient[20824]:
SYSTEM_USER:'oscar', MYSQL_USER:'my_oscar', CONNECTION_ID:23,
DB_SERVER:'127.0.0.1', DB:'--', QUERY:'USE test;'
Mar 7 12:39:28 myhost MysqlClient[20824]:
SYSTEM_USER:'oscar', MYSQL_USER:'my_oscar', CONNECTION_ID:23,
DB_SERVER:'127.0.0.1', DB:'test', QUERY:'SHOW TABLES;'
MYSQL CLIENT SERVER-SIDE HELP
mysql> help search_string
If you provide an argument to the help command, mysql uses it as a search string to access server-side
help from the contents of the MySQL Reference Manual. The proper operation of this command requires that
the help tables in the mysql database be initialized with help topic information (see Section 5.1.14,
“Server-Side Help Support”).
If there is no match for the search string, the search fails:
mysql> help me
Nothing found
Please try to run 'help contents' for a list of all accessible topics
Use help contents to see a list of the help categories:
mysql> help contents
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the
following categories:
Account Management
Administration
Data Definition
Data Manipulation
Data Types
Functions
Functions and Modifiers for Use with GROUP BY
Geographic Features
Language Structure
Plugins
Storage Engines
Stored Routines
Table Maintenance
Transactions
Triggers
If the search string matches multiple items, mysql shows a list of matching topics:
mysql> help logs
Many help items for your request exist.
To make a more specific request, please type 'help <item>',
where <item> is one of the following topics:
SHOW
SHOW BINARY LOGS
SHOW ENGINE
SHOW LOGS
Use a topic as the search string to see the help entry for that topic:
mysql> help show binary logs
Name: 'SHOW BINARY LOGS'
Description:
Syntax:
SHOW BINARY LOGS
SHOW MASTER LOGS
Lists the binary log files on the server. This statement is used as
part of the procedure described in [purge-binary-logs], that shows how
to determine which logs can be purged.
mysql> SHOW BINARY LOGS;
+---------------+-----------+
| Log_name | File_size |
+---------------+-----------+
| binlog.000015 | 724935 |
| binlog.000016 | 733481 |
+---------------+-----------+
The search string can contain the wildcard characters % and _. These have the same meaning as for
pattern-matching operations performed with the LIKE operator. For example, HELP rep% returns a list of
topics that begin with rep:
mysql> HELP rep%
Many help items for your request exist.
To make a more specific request, please type 'help <item>',
where <item> is one of the following
topics:
REPAIR TABLE
REPEAT FUNCTION
REPEAT LOOP
REPLACE
REPLACE FUNCTION
EXECUTING SQL STATEMENTS FROM A TEXT FILE
The mysql client typically is used interactively, like this:
shell> mysql db_name
However, it is also possible to put your SQL statements in a file and then tell mysql to read its input
from that file. To do so, create a text file text_file that contains the statements you wish to execute.
Then invoke mysql as shown here:
shell> mysql db_name < text_file
If you place a USE db_name statement as the first statement in the file, it is unnecessary to specify the
database name on the command line:
shell> mysql < text_file
If you are already running mysql, you can execute an SQL script file using the source command or \.
command:
mysql> source file_name
mysql> \. file_name
Sometimes you may want your script to display progress information to the user. For this you can insert
statements like this:
SELECT '<info_to_display>' AS ' ';
The statement shown outputs <info_to_display>.
You can also invoke mysql with the --verbose option, which causes each statement to be displayed before
the result that it produces.
mysql ignores Unicode byte order mark (BOM) characters at the beginning of input files. Previously, it
read them and sent them to the server, resulting in a syntax error. Presence of a BOM does not cause
mysql to change its default character set. To do that, invoke mysql with an option such as
--default-character-set=utf8.
For more information about batch mode, see Section 3.5, “Using mysql in Batch Mode”.
MYSQL CLIENT TIPS
This section provides information about techniques for more effective use of mysql and about mysql
operational behavior.
• Input-Line Editing
• Disabling Interactive History
• Unicode Support on Windows
• Displaying Query Results Vertically
• Using Safe-Updates Mode (--safe-updates)
• Disabling mysql Auto-Reconnect
• mysql Client Parser Versus Server Parser
Input-Line Editing
mysql supports input-line editing, which enables you to modify the current input line in place or recall
previous input lines. For example, the left-arrow and right-arrow keys move horizontally within the
current input line, and the up-arrow and down-arrow keys move up and down through the set of previously
entered lines. Backspace deletes the character before the cursor and typing new characters enters them
at the cursor position. To enter the line, press Enter.
On Windows, the editing key sequences are the same as supported for command editing in console windows.
On Unix, the key sequences depend on the input library used to build mysql (for example, the libedit or
readline library).
Documentation for the libedit and readline libraries is available online. To change the set of key
sequences permitted by a given input library, define key bindings in the library startup file. This is a
file in your home directory: .editrc for libedit and .inputrc for readline.
For example, in libedit, Control+W deletes everything before the current cursor position and Control+U
deletes the entire line. In readline, Control+W deletes the word before the cursor and Control+U deletes
everything before the current cursor position. If mysql was built using libedit, a user who prefers the
readline behavior for these two keys can put the following lines in the .editrc file (creating the file
if necessary):
bind "^W" ed-delete-prev-word
bind "^U" vi-kill-line-prev
To see the current set of key bindings, temporarily put a line that says only bind at the end of .editrc.
Then mysql shows the bindings when it starts. Disabling Interactive History
The up-arrow key enables you to recall input lines from current and previous sessions. In cases where a
console is shared, this behavior may be unsuitable. mysql supports disabling the interactive history
partially or fully, depending on the host platform.
On Windows, the history is stored in memory. Alt+F7 deletes all input lines stored in memory for the
current history buffer. It also deletes the list of sequential numbers in front of the input lines
displayed with F7 and recalled (by number) with F9. New input lines entered after you press Alt+F7
repopulate the current history buffer. Clearing the buffer does not prevent logging to the Windows Event
Viewer, if the --syslog option was used to start mysql. Closing the console window also clears the
current history buffer.
To disable interactive history on Unix, first delete the .mysql_history file, if it exists (previous
entries are recalled otherwise). Then start mysql with the --histignore="*" option to ignore all new
input lines. To re-enable the recall (and logging) behavior, restart mysql without the option.
If you prevent the .mysql_history file from being created (see Controlling the History File) and use
--histignore="*" to start the mysql client, the interactive history recall facility is disabled fully.
Alternatively, if you omit the --histignore option, you can recall the input lines entered during the
current session. Unicode Support on Windows
Windows provides APIs based on UTF-16LE for reading from and writing to the console; the mysql client for
Windows is able to use these APIs. The Windows installer creates an item in the MySQL menu named MySQL
command line client - Unicode. This item invokes the mysql client with properties set to communicate
through the console to the MySQL server using Unicode.
To take advantage of this support manually, run mysql within a console that uses a compatible Unicode
font and set the default character set to a Unicode character set that is supported for communication
with the server:
1. Open a console window.
2. Go to the console window properties, select the font tab, and choose Lucida Console or some other
compatible Unicode font. This is necessary because console windows start by default using a DOS
raster font that is inadequate for Unicode.
3. Execute mysql.exe with the --default-character-set=utf8 (or utf8mb4) option. This option is necessary
because utf16le is one of the character sets that cannot be used as the client character set. See the
section called “Impermissible Client Character Sets”.
With those changes, mysql can use the Windows APIs to communicate with the console using UTF-16LE, and
communicate with the server using UTF-8. (The menu item mentioned previously sets the font and character
set as just described.)
To avoid those steps each time you run mysql, you can create a shortcut that invokes mysql.exe. The
shortcut should set the console font to Lucida Console or some other compatible Unicode font, and pass
the --default-character-set=utf8 (or utf8mb4) option to mysql.exe.
Alternatively, create a shortcut that only sets the console font, and set the character set in the
[mysql] group of your my.ini file:
[mysql]
default-character-set=utf8
Displaying Query Results Vertically
Some query results are much more readable when displayed vertically, instead of in the usual horizontal
table format. Queries can be displayed vertically by terminating the query with \G instead of a
semicolon. For example, longer text values that include newlines often are much easier to read with
vertical output:
mysql> SELECT * FROM mails WHERE LENGTH(txt) < 300 LIMIT 300,1\G
*************************** 1. row ***************************
msg_nro: 3068
date: 2000-03-01 23:29:50
time_zone: +0200
mail_from: Jones
reply: jones@example.com
mail_to: "John Smith" <smith@example.com>
sbj: UTF-8
txt: >>>>> "John" == John Smith writes:
John> Hi. I think this is a good idea. Is anyone familiar
John> with UTF-8 or Unicode? Otherwise, I'll put this on my
John> TODO list and see what happens.
Yes, please do that.
Regards,
Jones
file: inbox-jani-1
hash: 190402944
1 row in set (0.09 sec)
Using Safe-Updates Mode (--safe-updates)
For beginners, a useful startup option is --safe-updates (or --i-am-a-dummy, which has the same effect).
Safe-updates mode is helpful for cases when you might have issued an UPDATE or DELETE statement but
forgotten the WHERE clause indicating which rows to modify. Normally, such statements update or delete
all rows in the table. With --safe-updates, you can modify rows only by specifying the key values that
identify them, or a LIMIT clause, or both. This helps prevent accidents. Safe-updates mode also restricts
SELECT statements that produce (or are estimated to produce) very large result sets.
The --safe-updates option causes mysql to execute the following statement when it connects to the MySQL
server, to set the session values of the sql_safe_updates, sql_select_limit, and max_join_size system
variables:
SET sql_safe_updates=1, sql_select_limit=1000, max_join_size=1000000;
The SET statement affects statement processing as follows:
• Enabling sql_safe_updates causes UPDATE and DELETE statements to produce an error if they do not
specify a key constraint in the WHERE clause, or provide a LIMIT clause, or both. For example:
UPDATE tbl_name SET not_key_column=val WHERE key_column=val;
UPDATE tbl_name SET not_key_column=val LIMIT 1;
• Setting sql_select_limit to 1,000 causes the server to limit all SELECT result sets to 1,000 rows
unless the statement includes a LIMIT clause.
• Setting max_join_size to 1,000,000 causes multiple-table SELECT statements to produce an error if the
server estimates it must examine more than 1,000,000 row combinations.
To specify result set limits different from 1,000 and 1,000,000, you can override the defaults by using
the --select-limit and --max-join-size options when you invoke mysql:
mysql --safe-updates --select-limit=500 --max-join-size=10000
It is possible for UPDATE and DELETE statements to produce an error in safe-updates mode even with a key
specified in the WHERE clause, if the optimizer decides not to use the index on the key column:
• Range access on the index cannot be used if memory usage exceeds that permitted by the
range_optimizer_max_mem_size system variable. The optimizer then falls back to a table scan. See the
section called “Limiting Memory Use for Range Optimization”.
• If key comparisons require type conversion, the index may not be used (see Section 8.3.1, “How MySQL
Uses Indexes”). Suppose that an indexed string column c1 is compared to a numeric value using WHERE
c1 = 2222. For such comparisons, the string value is converted to a number and the operands are
compared numerically (see Section 12.3, “Type Conversion in Expression Evaluation”), preventing use
of the index. If safe-updates mode is enabled, an error occurs.
As of MySQL 5.7.25, safe-updates mode also includes these behaviors:
• EXPLAIN with UPDATE and DELETE statements does not produce safe-updates errors. This enables use of
EXPLAIN plus SHOW WARNINGS to see why an index is not used, which can be helpful in cases such as
when a range_optimizer_max_mem_size violation or type conversion occurs and the optimizer does not
use an index even though a key column was specified in the WHERE clause.
• When a safe-updates error occurs, the error message includes the first diagnostic that was produced,
to provide information about the reason for failure. For example, the message may indicate that the
range_optimizer_max_mem_size value was exceeded or type conversion occurred, either of which can
preclude use of an index.
• For multiple-table deletes and updates, an error is produced with safe updates enabled only if any
target table uses a table scan.
Disabling mysql Auto-Reconnect
If the mysql client loses its connection to the server while sending a statement, it immediately and
automatically tries to reconnect once to the server and send the statement again. However, even if mysql
succeeds in reconnecting, your first connection has ended and all your previous session objects and
settings are lost: temporary tables, the autocommit mode, and user-defined and session variables. Also,
any current transaction rolls back. This behavior may be dangerous for you, as in the following example
where the server was shut down and restarted between the first and second statements without you knowing
it:
mysql> SET @a=1;
Query OK, 0 rows affected (0.05 sec)
mysql> INSERT INTO t VALUES(@a);
ERROR 2006: MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 1
Current database: test
Query OK, 1 row affected (1.30 sec)
mysql> SELECT * FROM t;
+------+
| a |
+------+
| NULL |
+------+
1 row in set (0.05 sec)
The @a user variable has been lost with the connection, and after the reconnection it is undefined. If it
is important to have mysql terminate with an error if the connection has been lost, you can start the
mysql client with the --skip-reconnect option.
For more information about auto-reconnect and its effect on state information when a reconnection occurs,
see C API Automatic Reconnection Control[5]. mysql Client Parser Versus Server Parser
The mysql client uses a parser on the client side that is not a duplicate of the complete parser used by
the mysqld server on the server side. This can lead to differences in treatment of certain constructs.
Examples:
• The server parser treats strings delimited by " characters as identifiers rather than as plain
strings if the ANSI_QUOTES SQL mode is enabled.
The mysql client parser does not take the ANSI_QUOTES SQL mode into account. It treats strings
delimited by ", ', and ` characters the same, regardless of whether ANSI_QUOTES is enabled.
• Within /*! ... */ comments, the mysql client parser interprets short-form mysql commands. The server
parser does not interpret them because these commands have no meaning on the server side.
If it is desirable for mysql not to interpret short-form commands within comments, a partial
workaround is to use the --binary-mode option, which causes all mysql commands to be disabled except
\C and \d in noninteractive mode (for input piped to mysql or loaded using the source command).
COPYRIGHT
Copyright © 1997, 2020, Oracle and/or its affiliates.
This documentation is free software; you can redistribute it and/or modify it only under the terms of the
GNU General Public License as published by the Free Software Foundation; version 2 of the License.
This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
You should have received a copy of the GNU General Public License along with the program; if not, write
to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see
http://www.gnu.org/licenses/.
NOTES
1. MySQL Shell 8.0 (part of MySQL 8.0)
https://dev.mysql.com/doc/mysql-shell/8.0/en/
2. C API Data Structures
https://dev.mysql.com/doc/c-api/5.7/en/c-api-data-structures.html
3. C API Multiple Statement Execution Support
https://dev.mysql.com/doc/c-api/5.7/en/c-api-multiple-queries.html
4. mysql_change_user()
https://dev.mysql.com/doc/c-api/5.7/en/mysql-change-user.html
5. C API Automatic Reconnection Control
https://dev.mysql.com/doc/c-api/5.7/en/c-api-auto-reconnect.html
SEE ALSO
For more information, please refer to the MySQL Reference Manual, which may already be installed locally
and which is also available online at http://dev.mysql.com/doc/.
AUTHOR
Oracle Corporation (http://dev.mysql.com/).