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CREATE
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 } ] ... }
[, ... ]
] )
[ 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 may 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 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(5)].
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 may 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. However, inherited and new
column declarations of the same name need not specify identical
constraints: all constraints provided from any declaration are merged
together and all are applied to the new table. 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.
LIKE parent_table [ { INCLUDING | EXCLUDING } { DEFAULTS | CONSTRAINTS } ]
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.
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 may 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 may 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 may 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 may reference multiple
columns.
Currently, CHECK expressions cannot contain subqueries nor refer to
variables other than columns of the current row.
] [ ON UPDATE action ] (column constraint)
REFERENCES reftable [ ( refcolumn ) ] [ MATCH matchtype ] [ ON DELETE action
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 may not 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 may 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 may be postponed
until the end of the transaction (using the SET CONSTRAINTS
[set_constraints(5)] 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(5)] command.
WITH ( storage_parameter [= value] [, ... ] )
This clause specifies optional storage parameters for a table or
index; see Storage Parameters [create_table(5)] 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(5)].
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(5)]
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 used, or the
database's default tablespace if default_tablespace is an empty
string.
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 used, or the database's
default tablespace if default_tablespace is an empty string.
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(5)]. The only storage
parameter currently available for tables is:
FILLFACTOR
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.
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(5)] 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 may only refer to the
column they apply to; only CHECK table constraints may 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(5)], DROP TABLE [drop_table(l)], CREATE TABLESPACE
[create_tablespace(l)]
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Index for
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