oracular (3) SQL::Statement.3pm.gz
NAME
SQL::Statement - SQL parsing and processing engine
SYNOPSIS
# ... depends on what you want to do, see below
DESCRIPTION
The SQL::Statement module implements a pure Perl SQL parsing and execution engine. While it by no means
implements full ANSI standard, it does support many features including column and table aliases, built-in
and user-defined functions, implicit and explicit joins, complex nested search conditions, and other
features.
SQL::Statement is a small embeddable Database Management System (DBMS). This means that it provides all
of the services of a simple DBMS except that instead of a persistent storage mechanism, it has two
things: 1) an in-memory storage mechanism that allows you to prepare, execute, and fetch from SQL
statements using temporary tables and 2) a set of software sockets where any author can plug in any
storage mechanism.
There are three main uses for SQL::Statement. One or another (hopefully not all) may be irrelevant for
your needs: 1) to access and manipulate data in CSV, XML, and other formats 2) to build your own DBD for
a new data source 3) to parse and examine the structure of SQL statements.
INSTALLATION
There are no prerequisites for using this as a standalone parser. If you want to access persistent stored
data, you either need to write a subclass or use one of the DBI DBD drivers. You can install this module
using CPAN.pm, CPANPLUS.pm, PPM, apt-get, or other packaging tools or you can download the tar.gz file
from CPAN and use the standard perl mantra:
perl Makefile.PL
make
make test
make install
It works fine on all platforms it has been tested on. On Windows, you can use ppm or with the mantra use
nmake, dmake, or make depending on which is available.
USAGE
How can I use SQL::Statement to access and modify data?
SQL::Statement provides the SQL engine for a number of existing DBI drivers including DBD::CSV, DBD::DBM,
DBD::AnyData, DBD::Excel, DBD::Amazon, and others.
These modules provide access to Comma Separated Values, Fixed Length, XML, HTML and many other kinds of
text files, to Excel Spreadsheets, to BerkeleyDB and other DBM formats, and to non-traditional data
sources like on-the-fly Amazon searches.
If you are interested in accessing and manipulating persistent data, you may not really want to use
SQL::Statement directly, but use DBI along with one of the DBDs mentioned above instead. You will be
using SQL::Statement, but under the hood of the DBD. See <http://dbi.perl.org> for help with DBI and see
SQL::Statement::Syntax for a description of the SQL syntax that SQL::Statement provides for these modules
and see the documentation for whichever DBD you are using for additional details.
How can I use it to parse and examine the structure of SQL statements?
SQL::Statement can be used stand-alone (without a subclass and without DBI) to parse and examine the
structure of SQL statements. See SQL::Statement::Structure for details.
How can I use it to embed a SQL engine in a DBD or other module?
SQL::Statement is designed to be easily embedded in other modules and is especially suited for developing
new DBI drivers (DBDs). See SQL::Statement::Embed.
What SQL Syntax is supported?
SQL::Statement supports a small but powerful subset of SQL commands. See SQL::Statement::Syntax.
How can I extend the supported SQL syntax?
You can modify and extend the SQL syntax either by issuing SQL commands or by subclassing SQL::Statement.
See SQL::Statement::Syntax.
How can I participate in ongoing development?
SQL::Statement is a large module with many potential future directions. You are invited to help plan,
code, test, document, or kibbitz about these directions. If you want to join the development team, or
just hear more about the development, write Jeff (<jzuckerATcpan.org>) or Jens (<rehsackATcpan.org>) a
note.
METHODS
The following methods can or must be overridden by derived classes.
capability
$has_capability = $h->capability('capability_name');
Returns a true value if the specified capability is available.
Currently no capabilities are defined and this is a placeholder for future use. It is envisioned it will
be used like "SQL::Eval::Table::capability".
open_table
The "open_table" method must be overridden by derived classes to provide the capability of opening data
tables. This is a necessity.
Arguments given to open_table call:
$data
The database memo parameter. See "execute".
$table
The name of the table to open as parsed from SQL statement.
$createMode
A flag indicating the mode ("CREATE TABLE ...") the table should be opened with. Set to a true value
in create mode.
$lockMode
A flag indicating whether the table should be opened for writing (any other than "SELECT ..."). Set
to a true value if the table is to be opened for write access.
The following methods are required to use SQL::Statement in a DBD (for example).
new
Instantiates a new SQL::Statement object.
Arguments:
$sql
The SQL statement for later actions.
$parser
An instance of a SQL::Parser object or flags for it's instantiation. If omitted, default flags are
used.
When the basic initialization is completed, "$self->prepare($sql, $parser)" is invoked.
prepare
Prepares SQL::Statement to execute a SQL statement.
Arguments:
$sql
The SQL statement to parse and prepare.
$parser
Instance of a SQL::Parser object to parse the provided SQL statement.
execute
Executes a prepared statement.
Arguments:
$data
Memo field passed through to calls of the instantiated $table objects or "open_table" calls. In
"CREATE" with subquery, "$data->{Database}" must be a DBI database handle object.
$params
Bound params via DBI ...
errstr
Gives the error string of the last error, if any.
fetch_row
Fetches the next row from the result data set (implies removing the fetched row from the result data
set).
fetch_rows
Fetches all (remaining) rows from the result data set.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc SQL::Statement
You can also look for information at:
• RT: CPAN's request tracker
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=SQL-Statement>
• AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/SQL-Statement>
• CPAN Ratings
<http://cpanratings.perl.org/s/SQL-Statement>
• CPAN Search
<http://search.cpan.org/dist/SQL-Statement/>
Where can I go for help?
For questions about installation or usage, please ask on the dbi-users@perl.org mailing list (see
http://dbi.perl.org) or post a question on PerlMonks (<http://www.perlmonks.org/>, where Jeff is known as
jZed). Jens does not visit PerlMonks on a regular basis.
If you have a bug report, a patch or a suggestion, please open a new report ticket at CPAN (but please
check previous reports first in case your issue has already been addressed). You can mail any of the
module maintainers, but you are more assured of an answer by posting to the dbi-users list or reporting
the issue in RT.
Report tickets should contain a detailed description of the bug or enhancement request and at least an
easily verifiable way of reproducing the issue or fix. Patches are always welcome, too.
Where can I go for help with a concrete version?
Bugs and feature requests are accepted against the latest version only. To get patches for earlier
versions, you need to get an agreement with a developer of your choice - who may or not report the issue
and a suggested fix upstream (depends on the license you have chosen).
Business support and maintenance
For business support you can contact Jens via his CPAN email address rehsackATcpan.org. Please keep in
mind that business support is neither available for free nor are you eligible to receive any support
based on the license distributed with this package.
ACKNOWLEDGEMENTS
Jochen Wiedmann created the original module as an XS (C) extension in 1998. Jeff Zucker took over the
maintenance in 2001 and rewrote all of the C portions in Perl and began extending the SQL support. More
recently Ilya Sterin provided help with SQL::Parser, Tim Bunce provided both general and specific
support, Dan Wright and Dean Arnold have contributed extensively to the code, and dozens of people from
around the world have submitted patches, bug reports, and suggestions.
In 2008 Jens Rehsack took over the maintenance of the extended module from Jeff. Together with H.Merijn
Brand (who has taken DBD::CSV), Detlef Wartke and Volker Schubbert (especially between 1.16 developer
versions until 1.22) and all submitters of bug reports via RT a lot of issues have been fixed.
Thanks to all!
If you're interested in helping develop SQL::Statement or want to use it with your own modules, feel free
to contact Jeff or Jens.
BUGS AND LIMITATIONS
• Currently we treat NULL and '' as the same in AnyData/CSV mode - eventually fix.
• No nested C-style comments allowed as SQL99 says.
• There are some issues regarding combining outer joins with where clauses.
• Aggregate functions cannot be used in where clause.
• Some SQL commands/features are not supported (most of them cannot by design), as "LOCK TABLE", using
indices, sub-selects etc.
Currently the statement for missing features is: I plan to create a SQL::Statement v2.00 based on a
pure Backus-Naur-Form parser and a fully object oriented command pattern based engine implementation.
When the time is available, I will do it. Until then bugs will be fixed or other Perl modules under
my maintainership will receive my time. Features which can be added without deep design changes might
be applied earlier - especially when their addition allows studying effective ways to implement the
feature in upcoming 2.00.
• Some people report that SQL::Statement is slower since the XS parts were implemented in pure Perl.
This might be true, but on the other hand a large number of features have been added including
support for ANSI SQL 99.
For SQL::Statement 1.xx it's not planned to add new XS parts.
• Wildcards are expanded to lower cased identifiers. This might confuse some people, but it was easier
to implement.
The warning in DBI to never trust the case of returned column names should be read more often. If you
need to rely on identifiers, always use "sth->{NAME_lc}" or "sth->{NAME_uc}" - never rely on
"sth->{NAME}":
$dbh->{FetchHashKeyName} = 'NAME_lc';
$sth = $dbh->prepare("SELECT FOO, BAR, ID, NAME, BAZ FROM TABLE");
$sth->execute;
$hash_ref = $sth->fetchall_hashref('id');
print "Name for id 42 is $hash_ref->{42}->{name}\n";
See "FetchHashKeyName" in DBI for more information.
• Unable to use the same table twice with different aliases. Workaround: Temporary tables: "CREATE TEMP
TABLE t_foo AS SELECT * FROM foo". Than both tables can be used independently.
Patches to fix bugs/limitations (or a grant to do it) would be very welcome. Please note, that any
patches must successfully pass all the "SQL::Statement", DBD::File and DBD::CSV tests and must be a
general improvement.
AUTHOR AND COPYRIGHT
Jochen Wiedmann created the original module as an XS (C) extension in 1998. Jeff Zucker took over the
maintenance in 2001 and rewrote all of the C portions in perl and began extending the SQL support. Since
2008, Jens Rehsack is the maintainer.
Copyright (c) 2001,2005 by Jeff Zucker: jzuckerATcpan.org Copyright (c) 2007-2020 by Jens Rehsack:
rehsackATcpan.org
Portions Copyright (C) 1998 by Jochen Wiedmann: jwiedATcpan.org
All rights reserved.
LICENSE
You may distribute this module under the terms of either the GNU General Public License or the Artistic
License, as specified in the Perl README file.