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 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, 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 notational 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 referenced 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 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. 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 CONSTRAINTS is
specified; other types of constraints will never be copied.
Also, no distinction is made between column 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 table 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 referenced
columns using the given match type. There are three match types:
MATCH FULL, MATCH PARTIAL, and MATCH SIMPLE, 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 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 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 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. 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 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 [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 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 or PRIMARY KEY 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 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 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, toast.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, toast.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 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
autovacuum_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 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 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 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 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 constraints 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 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.
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)]