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CREATE TABLE(7) SQL Commands CREATE TABLE(7)
NAME
CREATE TABLE - define a new table
SYNOPSIS
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE table_name ( [
{ column_name data_type [ DEFAULT default_expr ] [ column_constraint [ ... ] ]
| table_constraint
| LIKE parent_table [ { INCLUDING | EXCLUDING } { DEFAULTS | CONSTRAINTS | INDEXES } ] ... }
[, ... ]
] )
[ INHERITS ( parent_table [, ... ] ) ]
[ WITH ( storage_parameter [= value] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE tablespace ]
where column_constraint is:
[ CONSTRAINT constraint_name ]
{ NOT NULL |
NULL |
UNIQUE index_parameters |
PRIMARY KEY index_parameters |
CHECK ( expression ) |
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 ]
{ UNIQUE ( column_name [, ... ] ) index_parameters |
PRIMARY KEY ( column_name [, ... ] ) index_parameters |
CHECK ( expression ) |
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 ]
index_parameters in UNIQUE and PRIMARY KEY constraints are:
[ WITH ( storage_parameter [= value] [, ... ] ) ]
[ USING INDEX TABLESPACE tablespace ]
DESCRIPTION
CREATE TABLE will create a new, initially empty table in the current database. The table will be owned by the user issu-
ing 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 can-
not be given when creating a temporary table. The name of the table must be distinct from the name of any other table,
sequence, index, or view 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 nota-
tional convenience for use when the constraint only affects one column.
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 refer-
enced with schema-qualified names. Any indexes created on a temporary table are automatically temporary as well.
Optionally, GLOBAL or LOCAL can be written before TEMPORARY or TEMP. This makes no difference in PostgreSQL, but
see Compatibility [create_table(7)].
table_name
The name (optionally schema-qualified) of the table to be created.
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 in the documentation.
DEFAULT
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.
INHERITS ( parent_table [, ... ] )
The optional INHERITS clause specifies a list of tables from which the new table automatically inherits all col-
umns.
Use of INHERITS creates a persistent relationship between the new child table and its parent table(s). Schema mod-
ifications 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 ta-
ble definition contain identically-named CHECK constraints, these constraints must all have the same check expres-
sion, or an error will be reported. Constraints having the same name and expression will be merged into one copy.
Notice that an unnamed CHECK constraint in the new table will never be merged, since a unique name will always be
chosen for it.
LIKE parent_table [ { INCLUDING | EXCLUDING } { DEFAULTS | CONSTRAINTS | INDEXES } ]
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 only be copied 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.
Not-null constraints are always copied to the new table. CHECK constraints will only be copied if INCLUDING CON-
STRAINTS is specified; other types of constraints will never be copied. Also, no distinction is made between col-
umn constraints and table constraints -- when constraints are requested, all check constraints are copied.
Any indexes on the original table will not be created on the new table, unless the INCLUDING INDEXES clause is
specified.
Note also that unlike INHERITS, copied columns and constraints are not merged with similarly named columns and
constraints. If the same name is specified explicitly or in another LIKE clause, an error is signalled.
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.
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. Technically, PRIMARY KEY is merely a combination of UNIQUE and NOT NULL, but identifying a set of
columns as primary key also provides metadata about the design of the schema, as a primary key implies that other
tables can rely on this set of columns as a unique identifier for rows.
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 other sets of columns named by any
unique constraint defined for the same table.
CHECK ( expression )
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.
REFERENCES reftable [ ( refcolumn ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE action ] (column constraint)
FOREIGN KEY ( column [, ... ] )
These clauses specify a foreign key constraint, which requires that a group of one or more columns of the new ta-
ble must only contain values that match values in the referenced column(s) of some row of the referenced table. If
refcolumn is omitted, the primary key of the reftable is used. The referenced columns must be the columns of a
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 refer-
enced columns using the given match type. There are three match types: MATCH FULL, MATCH PARTIAL, and MATCH SIM-
PLE, which is also the default. MATCH FULL will not allow one column of a multicolumn foreign key to be null
unless all foreign key columns are null. MATCH SIMPLE allows some foreign key columns to be null while other
parts of the foreign key are not null. MATCH PARTIAL is not yet implemented.
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 ta-
ble 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 value of the referencing column to the new value
of the referenced column, respectively.
SET NULL
Set the referencing column(s) to null.
SET DEFAULT
Set the referencing column(s) to their default values.
If the referenced column(s) are changed frequently, it might be wise to add an index to the foreign key column so that
referential actions associated with the foreign key column 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 immedi-
ately 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. Only foreign
key constraints currently accept this clause. All other constraint types 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 [create_table(7)]
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 configura-
tion 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 post-
pone 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 auto-
matic TRUNCATE [truncate(7)] is done at each commit.
DROP The temporary table will be dropped at the end of the current transaction block.
TABLESPACE tablespace
The tablespace 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
This clause allows selection of the tablespace in which the index associated with a UNIQUE or PRIMARY KEY con-
straint 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 or PRIMARY KEY con-
straint. Storage parameters for indexes are documented in CREATE INDEX [create_index(7)]. The storage parameters cur-
rently 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 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 remain-
ing 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_vac-
uum_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 cur-
rently estimated to be in the relation. If false, this table will not be autovacuumed, except to prevent transac-
tion Id wraparound. See 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 autovac-
uum_freeze_min_age larger than the half 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 autovac-
uum_freeze_max_age larger than the system-wide setting (it can only be set smaller). Note that while you can set
autovacuum_freeze_max_age very small, or even zero, this is usually unwise since it will force frequent vacuuming.
autovacuum_freeze_table_age, toast.autovacuum_freeze_table_age (integer)
Custom vacuum_freeze_table_age parameter.
NOTES
Using OIDs in new applications is not recommended: where possible, using a SERIAL or other sequence generator as the ta-
ble'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 inher-
itance 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 cinemas in tablespace diskvol1:
CREATE TABLE cinemas (
id serial,
name text,
location text
) TABLESPACE diskvol1;
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 tem-
porary 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 struc-
ture.
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 standard's distinction between global and local temporary tables is not in PostgreSQL, since that distinction depends
on the concept of modules, which PostgreSQL does not have. For compatibility's sake, PostgreSQL will accept the GLOBAL
and LOCAL keywords in a temporary table declaration, but they have no effect.
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.
COLUMN CHECK CONSTRAINTS
The SQL standard says that CHECK column constraints can only refer to the column they apply to; only CHECK table con-
straints can refer to multiple columns. PostgreSQL does not enforce this restriction; it treats column and table check
constraints alike.
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 inher-
itance 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 disal-
lowing them creates odd special cases for ALTER TABLE DROP COLUMN, so it seems cleaner to ignore this spec restriction.
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.
SEE ALSO
ALTER TABLE [alter_table(7)], DROP TABLE [drop_table(7)], CREATE TABLESPACE [create_tablespace(7)]
SQL - Language Statements 2011-09-22 CREATE TABLE(7)
