Provided by: postgresql-client-9.3_9.3.24-0ubuntu0.14.04_amd64 
NAME
CREATE_TABLE - define a new table
SYNOPSIS
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name ( [
{ column_name data_type [ COLLATE collation ] [ column_constraint [ ... ] ]
| table_constraint
| LIKE source_table [ like_option ... ] }
[, ... ]
] )
[ INHERITS ( parent_table [, ... ] ) ]
[ WITH ( storage_parameter [= value] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE tablespace_name ]
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name
OF type_name [ (
{ column_name WITH OPTIONS [ column_constraint [ ... ] ]
| table_constraint }
[, ... ]
) ]
[ WITH ( storage_parameter [= value] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE tablespace_name ]
where column_constraint is:
[ CONSTRAINT constraint_name ]
{ NOT NULL |
NULL |
CHECK ( expression ) [ NO INHERIT ] |
DEFAULT default_expr |
UNIQUE index_parameters |
PRIMARY KEY index_parameters |
REFERENCES reftable [ ( refcolumn ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]
[ ON DELETE action ] [ ON UPDATE action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
and table_constraint is:
[ CONSTRAINT constraint_name ]
{ CHECK ( expression ) [ NO INHERIT ] |
UNIQUE ( column_name [, ... ] ) index_parameters |
PRIMARY KEY ( column_name [, ... ] ) index_parameters |
EXCLUDE [ USING index_method ] ( exclude_element WITH operator [, ... ] ) index_parameters [ WHERE ( predicate ) ] |
FOREIGN KEY ( column_name [, ... ] ) REFERENCES reftable [ ( refcolumn [, ... ] ) ]
[ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE action ] [ ON UPDATE action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
and like_option is:
{ INCLUDING | EXCLUDING } { DEFAULTS | CONSTRAINTS | INDEXES | STORAGE | COMMENTS | ALL }
index_parameters in UNIQUE, PRIMARY KEY, and EXCLUDE constraints are:
[ WITH ( storage_parameter [= value] [, ... ] ) ]
[ USING INDEX TABLESPACE tablespace_name ]
exclude_element in an EXCLUDE constraint is:
{ column_name | ( expression ) } [ opclass ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ]
DESCRIPTION
CREATE TABLE will create a new, initially empty table in the current database. The table
will be owned by the user issuing the command.
If a schema name is given (for example, CREATE TABLE myschema.mytable ...) then the table
is created in the specified schema. Otherwise it is created in the current schema.
Temporary tables exist in a special schema, so a schema name cannot be given when creating
a temporary table. The name of the table must be distinct from the name of any other
table, sequence, index, view, or foreign table in the same schema.
CREATE TABLE also automatically creates a data type that represents the composite type
corresponding to one row of the table. Therefore, tables cannot have the same name as any
existing data type in the same schema.
The optional constraint clauses specify constraints (tests) that new or updated rows must
satisfy for an insert or update operation to succeed. A constraint is an SQL object that
helps define the set of valid values in the table in various ways.
There are two ways to define constraints: table constraints and column constraints. A
column constraint is defined as part of a column definition. A table constraint definition
is not tied to a particular column, and it can encompass more than one column. Every
column constraint can also be written as a table constraint; a column constraint is only a
notational convenience for use when the constraint only affects one column.
To be able to create a table, you must have USAGE privilege on all column types or the
type in the OF clause, respectively.
PARAMETERS
TEMPORARY or TEMP
If specified, the table is created as a temporary table. Temporary tables are
automatically dropped at the end of a session, or optionally at the end of the current
transaction (see ON COMMIT below). Existing permanent tables with the same name are
not visible to the current session while the temporary table exists, unless they are
referenced with schema-qualified names. Any indexes created on a temporary table are
automatically temporary as well.
The autovacuum daemon cannot access and therefore cannot vacuum or analyze temporary
tables. For this reason, appropriate vacuum and analyze operations should be performed
via session SQL commands. For example, if a temporary table is going to be used in
complex queries, it is wise to run ANALYZE on the temporary table after it is
populated.
Optionally, GLOBAL or LOCAL can be written before TEMPORARY or TEMP. This presently
makes no difference in PostgreSQL and is deprecated; see COMPATIBILITY.
UNLOGGED
If specified, the table is created as an unlogged table. Data written to unlogged
tables is not written to the write-ahead log (see Chapter 29, Reliability and the
Write-Ahead Log, in the documentation), which makes them considerably faster than
ordinary tables. However, they are not crash-safe: an unlogged table is automatically
truncated after a crash or unclean shutdown. The contents of an unlogged table are
also not replicated to standby servers. Any indexes created on an unlogged table are
automatically unlogged as well.
IF NOT EXISTS
Do not throw an error if a relation with the same name already exists. A notice is
issued in this case. Note that there is no guarantee that the existing relation is
anything like the one that would have been created.
table_name
The name (optionally schema-qualified) of the table to be created.
OF type_name
Creates a typed table, which takes its structure from the specified composite type
(name optionally schema-qualified). A typed table is tied to its type; for example the
table will be dropped if the type is dropped (with DROP TYPE ... CASCADE).
When a typed table is created, then the data types of the columns are determined by
the underlying composite type and are not specified by the CREATE TABLE command. But
the CREATE TABLE command can add defaults and constraints to the table and can specify
storage parameters.
column_name
The name of a column to be created in the new table.
data_type
The data type of the column. This can include array specifiers. For more information
on the data types supported by PostgreSQL, refer to Chapter 8, Data Types, in the
documentation.
COLLATE collation
The COLLATE clause assigns a collation to the column (which must be of a collatable
data type). If not specified, the column data type's default collation is used.
INHERITS ( parent_table [, ... ] )
The optional INHERITS clause specifies a list of tables from which the new table
automatically inherits all columns.
Use of INHERITS creates a persistent relationship between the new child table and its
parent table(s). Schema modifications to the parent(s) normally propagate to children
as well, and by default the data of the child table is included in scans of the
parent(s).
If the same column name exists in more than one parent table, an error is reported
unless the data types of the columns match in each of the parent tables. If there is
no conflict, then the duplicate columns are merged to form a single column in the new
table. If the column name list of the new table contains a column name that is also
inherited, the data type must likewise match the inherited column(s), and the column
definitions are merged into one. If the new table explicitly specifies a default value
for the column, this default overrides any defaults from inherited declarations of the
column. Otherwise, any parents that specify default values for the column must all
specify the same default, or an error will be reported.
CHECK constraints are merged in essentially the same way as columns: if multiple
parent tables and/or the new table definition contain identically-named CHECK
constraints, these constraints must all have the same check expression, or an error
will be reported. Constraints having the same name and expression will be merged into
one copy. A constraint marked NO INHERIT in a parent will not be considered. Notice
that an unnamed CHECK constraint in the new table will never be merged, since a unique
name will always be chosen for it.
Column STORAGE settings are also copied from parent tables.
LIKE source_table [ like_option ... ]
The LIKE clause specifies a table from which the new table automatically copies all
column names, their data types, and their not-null constraints.
Unlike INHERITS, the new table and original table are completely decoupled after
creation is complete. Changes to the original table will not be applied to the new
table, and it is not possible to include data of the new table in scans of the
original table.
Default expressions for the copied column definitions will be copied only if INCLUDING
DEFAULTS is specified. The default behavior is to exclude default expressions,
resulting in the copied columns in the new table having null defaults. Note that
copying defaults that call database-modification functions, such as nextval, may
create a functional linkage between the original and new tables.
Not-null constraints are always copied to the new table. CHECK constraints will be
copied only if INCLUDING CONSTRAINTS is specified. No distinction is made between
column constraints and table constraints.
Indexes, PRIMARY KEY, UNIQUE, and EXCLUDE constraints on the original table will be
created on the new table only if INCLUDING INDEXES is specified. Names for the new
indexes and constraints are chosen according to the default rules, regardless of how
the originals were named. (This behavior avoids possible duplicate-name failures for
the new indexes.)
STORAGE settings for the copied column definitions will be copied only if INCLUDING
STORAGE is specified. The default behavior is to exclude STORAGE settings, resulting
in the copied columns in the new table having type-specific default settings. For more
on STORAGE settings, see Section 58.2, “TOAST”, in the documentation.
Comments for the copied columns, constraints, and indexes will be copied only if
INCLUDING COMMENTS is specified. The default behavior is to exclude comments,
resulting in the copied columns and constraints in the new table having no comments.
INCLUDING ALL is an abbreviated form of INCLUDING DEFAULTS INCLUDING CONSTRAINTS
INCLUDING INDEXES INCLUDING STORAGE INCLUDING COMMENTS.
Note that unlike INHERITS, columns and constraints copied by LIKE are not merged with
similarly named columns and constraints. If the same name is specified explicitly or
in another LIKE clause, an error is signaled.
The LIKE clause can also be used to copy column definitions from views, foreign
tables, or composite types. Inapplicable options (e.g., INCLUDING INDEXES from a view)
are ignored.
CONSTRAINT constraint_name
An optional name for a column or table constraint. If the constraint is violated, the
constraint name is present in error messages, so constraint names like col must be
positive can be used to communicate helpful constraint information to client
applications. (Double-quotes are needed to specify constraint names that contain
spaces.) If a constraint name is not specified, the system generates a name.
NOT NULL
The column is not allowed to contain null values.
NULL
The column is allowed to contain null values. This is the default.
This clause is only provided for compatibility with non-standard SQL databases. Its
use is discouraged in new applications.
CHECK ( expression ) [ NO INHERIT ]
The CHECK clause specifies an expression producing a Boolean result which new or
updated rows must satisfy for an insert or update operation to succeed. Expressions
evaluating to TRUE or UNKNOWN succeed. Should any row of an insert or update operation
produce a FALSE result an error exception is raised and the insert or update does not
alter the database. A check constraint specified as a column constraint should
reference that column's value only, while an expression appearing in a table
constraint can reference multiple columns.
Currently, CHECK expressions cannot contain subqueries nor refer to variables other
than columns of the current row.
A constraint marked with NO INHERIT will not propagate to child tables.
DEFAULT default_expr
The DEFAULT clause assigns a default data value for the column whose column definition
it appears within. The value is any variable-free expression (subqueries and
cross-references to other columns in the current table are not allowed). The data type
of the default expression must match the data type of the column.
The default expression will be used in any insert operation that does not specify a
value for the column. If there is no default for a column, then the default is null.
UNIQUE (column constraint), UNIQUE ( column_name [, ... ] ) (table constraint)
The UNIQUE constraint specifies that a group of one or more columns of a table can
contain only unique values. The behavior of the unique table constraint is the same as
that for column constraints, with the additional capability to span multiple columns.
For the purpose of a unique constraint, null values are not considered equal.
Each unique table constraint must name a set of columns that is different from the set
of columns named by any other unique or primary key constraint defined for the table.
(Otherwise it would just be the same constraint listed twice.)
PRIMARY KEY (column constraint), PRIMARY KEY ( column_name [, ... ] ) (table constraint)
The PRIMARY KEY constraint specifies that a column or columns of a table can contain
only unique (non-duplicate), nonnull values. Only one primary key can be specified for
a table, whether as a column constraint or a table constraint.
The primary key constraint should name a set of columns that is different from the set
of columns named by any unique constraint defined for the same table. (Otherwise, the
unique constraint is redundant and will be discarded.)
PRIMARY KEY enforces the same data constraints as a combination of UNIQUE and NOT
NULL, but identifying a set of columns as the primary key also provides metadata about
the design of the schema, since a primary key implies that other tables can rely on
this set of columns as a unique identifier for rows.
EXCLUDE [ USING index_method ] ( exclude_element WITH operator [, ... ] ) index_parameters
[ WHERE ( predicate ) ]
The EXCLUDE clause defines an exclusion constraint, which guarantees that if any two
rows are compared on the specified column(s) or expression(s) using the specified
operator(s), not all of these comparisons will return TRUE. If all of the specified
operators test for equality, this is equivalent to a UNIQUE constraint, although an
ordinary unique constraint will be faster. However, exclusion constraints can specify
constraints that are more general than simple equality. For example, you can specify a
constraint that no two rows in the table contain overlapping circles (see Section 8.8,
“Geometric Types”, in the documentation) by using the && operator.
Exclusion constraints are implemented using an index, so each specified operator must
be associated with an appropriate operator class (see Section 11.9, “Operator Classes
and Operator Families”, in the documentation) for the index access method
index_method. The operators are required to be commutative. Each exclude_element can
optionally specify an operator class and/or ordering options; these are described
fully under CREATE INDEX (CREATE_INDEX(7)).
The access method must support amgettuple (see Chapter 54, Index Access Method
Interface Definition, in the documentation); at present this means GIN cannot be used.
Although it's allowed, there is little point in using B-tree or hash indexes with an
exclusion constraint, because this does nothing that an ordinary unique constraint
doesn't do better. So in practice the access method will always be GiST or SP-GiST.
The predicate allows you to specify an exclusion constraint on a subset of the table;
internally this creates a partial index. Note that parentheses are required around the
predicate.
REFERENCES reftable [ ( refcolumn ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE
action ] (column constraint), FOREIGN KEY ( column_name [, ... ] ) REFERENCES reftable [ (
refcolumn [, ... ] ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE action ]
(table constraint)
These clauses specify a foreign key constraint, which requires that a group of one or
more columns of the new table must only contain values that match values in the
referenced column(s) of some row of the referenced table. If the refcolumn list is
omitted, the primary key of the reftable is used. The referenced columns must be the
columns of a non-deferrable unique or primary key constraint in the referenced table.
Note that foreign key constraints cannot be defined between temporary tables and
permanent tables.
A value inserted into the referencing column(s) is matched against the values of the
referenced table and referenced columns using the given match type. There are three
match types: MATCH FULL, MATCH PARTIAL, and MATCH SIMPLE (which is the default).
MATCH FULL will not allow one column of a multicolumn foreign key to be null unless
all foreign key columns are null; if they are all null, the row is not required to
have a match in the referenced table. MATCH SIMPLE allows any of the foreign key
columns to be null; if any of them are null, the row is not required to have a match
in the referenced table. MATCH PARTIAL is not yet implemented. (Of course, NOT NULL
constraints can be applied to the referencing column(s) to prevent these cases from
arising.)
In addition, when the data in the referenced columns is changed, certain actions are
performed on the data in this table's columns. The ON DELETE clause specifies the
action to perform when a referenced row in the referenced table is being deleted.
Likewise, the ON UPDATE clause specifies the action to perform when a referenced
column in the referenced table is being updated to a new value. If the row is updated,
but the referenced column is not actually changed, no action is done. Referential
actions other than the NO ACTION check cannot be deferred, even if the constraint is
declared deferrable. There are the following possible actions for each clause:
NO ACTION
Produce an error indicating that the deletion or update would create a foreign key
constraint violation. If the constraint is deferred, this error will be produced
at constraint check time if there still exist any referencing rows. This is the
default action.
RESTRICT
Produce an error indicating that the deletion or update would create a foreign key
constraint violation. This is the same as NO ACTION except that the check is not
deferrable.
CASCADE
Delete any rows referencing the deleted row, or update the values of the
referencing column(s) to the new values of the referenced columns, respectively.
SET NULL
Set the referencing column(s) to null.
SET DEFAULT
Set the referencing column(s) to their default values. (There must be a row in the
referenced table matching the default values, if they are not null, or the
operation will fail.)
If the referenced column(s) are changed frequently, it might be wise to add an index
to the referencing column(s) so that referential actions associated with the foreign
key constraint can be performed more efficiently.
DEFERRABLE, NOT DEFERRABLE
This controls whether the constraint can be deferred. A constraint that is not
deferrable will be checked immediately after every command. Checking of constraints
that are deferrable can be postponed until the end of the transaction (using the SET
CONSTRAINTS (SET_CONSTRAINTS(7)) command). NOT DEFERRABLE is the default. Currently,
only UNIQUE, PRIMARY KEY, EXCLUDE, and REFERENCES (foreign key) constraints accept
this clause. NOT NULL and CHECK constraints are not deferrable.
INITIALLY IMMEDIATE, INITIALLY DEFERRED
If a constraint is deferrable, this clause specifies the default time to check the
constraint. If the constraint is INITIALLY IMMEDIATE, it is checked after each
statement. This is the default. If the constraint is INITIALLY DEFERRED, it is checked
only at the end of the transaction. The constraint check time can be altered with the
SET CONSTRAINTS (SET_CONSTRAINTS(7)) command.
WITH ( storage_parameter [= value] [, ... ] )
This clause specifies optional storage parameters for a table or index; see Storage
Parameters for more information. The WITH clause for a table can also include
OIDS=TRUE (or just OIDS) to specify that rows of the new table should have OIDs
(object identifiers) assigned to them, or OIDS=FALSE to specify that the rows should
not have OIDs. If OIDS is not specified, the default setting depends upon the
default_with_oids configuration parameter. (If the new table inherits from any tables
that have OIDs, then OIDS=TRUE is forced even if the command says OIDS=FALSE.)
If OIDS=FALSE is specified or implied, the new table does not store OIDs and no OID
will be assigned for a row inserted into it. This is generally considered worthwhile,
since it will reduce OID consumption and thereby postpone the wraparound of the 32-bit
OID counter. Once the counter wraps around, OIDs can no longer be assumed to be
unique, which makes them considerably less useful. In addition, excluding OIDs from a
table reduces the space required to store the table on disk by 4 bytes per row (on
most machines), slightly improving performance.
To remove OIDs from a table after it has been created, use ALTER TABLE
(ALTER_TABLE(7)).
WITH OIDS, WITHOUT OIDS
These are obsolescent syntaxes equivalent to WITH (OIDS) and WITH (OIDS=FALSE),
respectively. If you wish to give both an OIDS setting and storage parameters, you
must use the WITH ( ... ) syntax; see above.
ON COMMIT
The behavior of temporary tables at the end of a transaction block can be controlled
using ON COMMIT. The three options are:
PRESERVE ROWS
No special action is taken at the ends of transactions. This is the default
behavior.
DELETE ROWS
All rows in the temporary table will be deleted at the end of each transaction
block. Essentially, an automatic TRUNCATE(7) is done at each commit.
DROP
The temporary table will be dropped at the end of the current transaction block.
TABLESPACE tablespace_name
The tablespace_name is the name of the tablespace in which the new table is to be
created. If not specified, default_tablespace is consulted, or temp_tablespaces if the
table is temporary.
USING INDEX TABLESPACE tablespace_name
This clause allows selection of the tablespace in which the index associated with a
UNIQUE, PRIMARY KEY, or EXCLUDE constraint will be created. If not specified,
default_tablespace is consulted, or temp_tablespaces if the table is temporary.
Storage Parameters
The WITH clause can specify storage parameters for tables, and for indexes associated with
a UNIQUE, PRIMARY KEY, or EXCLUDE constraint. Storage parameters for indexes are
documented in CREATE INDEX (CREATE_INDEX(7)). The storage parameters currently available
for tables are listed below. For each parameter, unless noted, there is an additional
parameter with the same name prefixed with toast., which can be used to control the
behavior of the table's secondary TOAST table, if any (see Section 58.2, “TOAST”, in the
documentation for more information about TOAST). Note that the TOAST table inherits the
autovacuum_* values from its parent table, if there are no toast.autovacuum_* settings
set.
fillfactor (integer)
The fillfactor for a table is a percentage between 10 and 100. 100 (complete packing)
is the default. When a smaller fillfactor is specified, INSERT operations pack table
pages only to the indicated percentage; the remaining space on each page is reserved
for updating rows on that page. This gives UPDATE a chance to place the updated copy
of a row on the same page as the original, which is more efficient than placing it on
a different page. For a table whose entries are never updated, complete packing is the
best choice, but in heavily updated tables smaller fillfactors are appropriate. This
parameter cannot be set for TOAST tables.
autovacuum_enabled, toast.autovacuum_enabled (boolean)
Enables or disables the autovacuum daemon on a particular table. If true, the
autovacuum daemon will initiate a VACUUM operation on a particular table when the
number of updated or deleted tuples exceeds autovacuum_vacuum_threshold plus
autovacuum_vacuum_scale_factor times the number of live tuples currently estimated to
be in the relation. Similarly, it will initiate an ANALYZE operation when the number
of inserted, updated or deleted tuples exceeds autovacuum_analyze_threshold plus
autovacuum_analyze_scale_factor times the number of live tuples currently estimated to
be in the relation. If false, this table will not be autovacuumed, except to prevent
transaction Id wraparound. See Section 23.1.5, “Preventing Transaction ID Wraparound
Failures”, in the documentation for more about wraparound prevention. Observe that
this variable inherits its value from the autovacuum setting.
autovacuum_vacuum_threshold, toast.autovacuum_vacuum_threshold (integer)
Minimum number of updated or deleted tuples before initiate a VACUUM operation on a
particular table.
autovacuum_vacuum_scale_factor, toast.autovacuum_vacuum_scale_factor (float4)
Multiplier for reltuples to add to autovacuum_vacuum_threshold.
autovacuum_analyze_threshold (integer)
Minimum number of inserted, updated, or deleted tuples before initiate an ANALYZE
operation on a particular table.
autovacuum_analyze_scale_factor (float4)
Multiplier for reltuples to add to autovacuum_analyze_threshold.
autovacuum_vacuum_cost_delay, toast.autovacuum_vacuum_cost_delay (integer)
Custom autovacuum_vacuum_cost_delay parameter.
autovacuum_vacuum_cost_limit, toast.autovacuum_vacuum_cost_limit (integer)
Custom autovacuum_vacuum_cost_limit parameter.
autovacuum_freeze_min_age, toast.autovacuum_freeze_min_age (integer)
Custom vacuum_freeze_min_age parameter. Note that autovacuum will ignore attempts to
set a per-table autovacuum_freeze_min_age larger than half the system-wide
autovacuum_freeze_max_age setting.
autovacuum_freeze_max_age, toast.autovacuum_freeze_max_age (integer)
Custom autovacuum_freeze_max_age parameter. Note that autovacuum will ignore attempts
to set a per-table autovacuum_freeze_max_age larger than the system-wide setting (it
can only be set smaller).
autovacuum_freeze_table_age, toast.autovacuum_freeze_table_age (integer)
Custom vacuum_freeze_table_age parameter.
autovacuum_multixact_freeze_min_age, toast.autovacuum_multixact_freeze_min_age (integer)
Custom vacuum_multixact_freeze_min_age parameter. Note that autovacuum will ignore
attempts to set a per-table autovacuum_multixact_freeze_min_age larger than half the
system-wide autovacuum_multixact_freeze_max_age setting.
autovacuum_multixact_freeze_max_age, toast.autovacuum_multixact_freeze_max_age (integer)
Custom autovacuum_multixact_freeze_max_age parameter. Note that autovacuum will ignore
attempts to set a per-table autovacuum_multixact_freeze_max_age larger than the
system-wide setting (it can only be set smaller).
autovacuum_multixact_freeze_table_age, toast.autovacuum_multixact_freeze_table_age
(integer)
Custom vacuum_multixact_freeze_table_age parameter.
NOTES
Using OIDs in new applications is not recommended: where possible, using a SERIAL or other
sequence generator as the table's primary key is preferred. However, if your application
does make use of OIDs to identify specific rows of a table, it is recommended to create a
unique constraint on the oid column of that table, to ensure that OIDs in the table will
indeed uniquely identify rows even after counter wraparound. Avoid assuming that OIDs are
unique across tables; if you need a database-wide unique identifier, use the combination
of tableoid and row OID for the purpose.
Tip
The use of OIDS=FALSE is not recommended for tables with no primary key, since without
either an OID or a unique data key, it is difficult to identify specific rows.
PostgreSQL automatically creates an index for each unique constraint and primary key
constraint to enforce uniqueness. Thus, it is not necessary to create an index explicitly
for primary key columns. (See CREATE INDEX (CREATE_INDEX(7)) for more information.)
Unique constraints and primary keys are not inherited in the current implementation. This
makes the combination of inheritance and unique constraints rather dysfunctional.
A table cannot have more than 1600 columns. (In practice, the effective limit is usually
lower because of tuple-length constraints.)
EXAMPLES
Create table films and table distributors:
CREATE TABLE films (
code char(5) CONSTRAINT firstkey PRIMARY KEY,
title varchar(40) NOT NULL,
did integer NOT NULL,
date_prod date,
kind varchar(10),
len interval hour to minute
);
CREATE TABLE distributors (
did integer PRIMARY KEY DEFAULT nextval('serial'),
name varchar(40) NOT NULL CHECK (name <> '')
);
Create a table with a 2-dimensional array:
CREATE TABLE array_int (
vector int[][]
);
Define a unique table constraint for the table films. Unique table constraints can be
defined on one or more columns of the table:
CREATE TABLE films (
code char(5),
title varchar(40),
did integer,
date_prod date,
kind varchar(10),
len interval hour to minute,
CONSTRAINT production UNIQUE(date_prod)
);
Define a check column constraint:
CREATE TABLE distributors (
did integer CHECK (did > 100),
name varchar(40)
);
Define a check table constraint:
CREATE TABLE distributors (
did integer,
name varchar(40),
CONSTRAINT con1 CHECK (did > 100 AND name <> '')
);
Define a primary key table constraint for the table films:
CREATE TABLE films (
code char(5),
title varchar(40),
did integer,
date_prod date,
kind varchar(10),
len interval hour to minute,
CONSTRAINT code_title PRIMARY KEY(code,title)
);
Define a primary key constraint for table distributors. The following two examples are
equivalent, the first using the table constraint syntax, the second the column constraint
syntax:
CREATE TABLE distributors (
did integer,
name varchar(40),
PRIMARY KEY(did)
);
CREATE TABLE distributors (
did integer PRIMARY KEY,
name varchar(40)
);
Assign a literal constant default value for the column name, arrange for the default value
of column did to be generated by selecting the next value of a sequence object, and make
the default value of modtime be the time at which the row is inserted:
CREATE TABLE distributors (
name varchar(40) DEFAULT 'Luso Films',
did integer DEFAULT nextval('distributors_serial'),
modtime timestamp DEFAULT current_timestamp
);
Define two NOT NULL column constraints on the table distributors, one of which is
explicitly given a name:
CREATE TABLE distributors (
did integer CONSTRAINT no_null NOT NULL,
name varchar(40) NOT NULL
);
Define a unique constraint for the name column:
CREATE TABLE distributors (
did integer,
name varchar(40) UNIQUE
);
The same, specified as a table constraint:
CREATE TABLE distributors (
did integer,
name varchar(40),
UNIQUE(name)
);
Create the same table, specifying 70% fill factor for both the table and its unique index:
CREATE TABLE distributors (
did integer,
name varchar(40),
UNIQUE(name) WITH (fillfactor=70)
)
WITH (fillfactor=70);
Create table circles with an exclusion constraint that prevents any two circles from
overlapping:
CREATE TABLE circles (
c circle,
EXCLUDE USING gist (c WITH &&)
);
Create table cinemas in tablespace diskvol1:
CREATE TABLE cinemas (
id serial,
name text,
location text
) TABLESPACE diskvol1;
Create a composite type and a typed table:
CREATE TYPE employee_type AS (name text, salary numeric);
CREATE TABLE employees OF employee_type (
PRIMARY KEY (name),
salary WITH OPTIONS DEFAULT 1000
);
COMPATIBILITY
The CREATE TABLE command conforms to the SQL standard, with exceptions listed below.
Temporary Tables
Although the syntax of CREATE TEMPORARY TABLE resembles that of the SQL standard, the
effect is not the same. In the standard, temporary tables are defined just once and
automatically exist (starting with empty contents) in every session that needs them.
PostgreSQL instead requires each session to issue its own CREATE TEMPORARY TABLE command
for each temporary table to be used. This allows different sessions to use the same
temporary table name for different purposes, whereas the standard's approach constrains
all instances of a given temporary table name to have the same table structure.
The standard's definition of the behavior of temporary tables is widely ignored.
PostgreSQL's behavior on this point is similar to that of several other SQL databases.
The SQL standard also distinguishes between global and local temporary tables, where a
local temporary table has a separate set of contents for each SQL module within each
session, though its definition is still shared across sessions. Since PostgreSQL does not
support SQL modules, this distinction is not relevant in PostgreSQL.
For compatibility's sake, PostgreSQL will accept the GLOBAL and LOCAL keywords in a
temporary table declaration, but they currently have no effect. Use of these keywords is
discouraged, since future versions of PostgreSQL might adopt a more standard-compliant
interpretation of their meaning.
The ON COMMIT clause for temporary tables also resembles the SQL standard, but has some
differences. If the ON COMMIT clause is omitted, SQL specifies that the default behavior
is ON COMMIT DELETE ROWS. However, the default behavior in PostgreSQL is ON COMMIT
PRESERVE ROWS. The ON COMMIT DROP option does not exist in SQL.
Non-deferred Uniqueness Constraints
When a UNIQUE or PRIMARY KEY constraint is not deferrable, PostgreSQL checks for
uniqueness immediately whenever a row is inserted or modified. The SQL standard says that
uniqueness should be enforced only at the end of the statement; this makes a difference
when, for example, a single command updates multiple key values. To obtain
standard-compliant behavior, declare the constraint as DEFERRABLE but not deferred (i.e.,
INITIALLY IMMEDIATE). Be aware that this can be significantly slower than immediate
uniqueness checking.
Column Check Constraints
The SQL standard says that CHECK column constraints can only refer to the column they
apply to; only CHECK table constraints can refer to multiple columns. PostgreSQL does not
enforce this restriction; it treats column and table check constraints alike.
EXCLUDE Constraint
The EXCLUDE constraint type is a PostgreSQL extension.
NULL “Constraint”
The NULL “constraint” (actually a non-constraint) is a PostgreSQL extension to the SQL
standard that is included for compatibility with some other database systems (and for
symmetry with the NOT NULL constraint). Since it is the default for any column, its
presence is simply noise.
Inheritance
Multiple inheritance via the INHERITS clause is a PostgreSQL language extension. SQL:1999
and later define single inheritance using a different syntax and different semantics.
SQL:1999-style inheritance is not yet supported by PostgreSQL.
Zero-column Tables
PostgreSQL allows a table of no columns to be created (for example, CREATE TABLE foo();).
This is an extension from the SQL standard, which does not allow zero-column tables.
Zero-column tables are not in themselves very useful, but disallowing them creates odd
special cases for ALTER TABLE DROP COLUMN, so it seems cleaner to ignore this spec
restriction.
LIKE Clause
While a LIKE clause exists in the SQL standard, many of the options that PostgreSQL
accepts for it are not in the standard, and some of the standard's options are not
implemented by PostgreSQL.
WITH Clause
The WITH clause is a PostgreSQL extension; neither storage parameters nor OIDs are in the
standard.
Tablespaces
The PostgreSQL concept of tablespaces is not part of the standard. Hence, the clauses
TABLESPACE and USING INDEX TABLESPACE are extensions.
Typed Tables
Typed tables implement a subset of the SQL standard. According to the standard, a typed
table has columns corresponding to the underlying composite type as well as one other
column that is the “self-referencing column”. PostgreSQL does not support these
self-referencing columns explicitly, but the same effect can be had using the OID feature.
SEE ALSO
ALTER TABLE (ALTER_TABLE(7)), DROP TABLE (DROP_TABLE(7)), CREATE TABLE AS
(CREATE_TABLE_AS(7)), CREATE TABLESPACE (CREATE_TABLESPACE(7)), CREATE TYPE
(CREATE_TYPE(7))