PostgreSQL - SQL Language Reference

PostgreSQL Reference Manual - Volume 1 - SQL Language Reference
by The PostgreSQL Global Development Group
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12.46 CREATE TABLE AS

Name

CREATE TABLE AS -- define a new table from the results of a query

Synopsis

CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE
 table_name
    [ (column_name [, ...] ) ]
    [ WITH ( storage_parameter [= value] [, ... ] ) | WITH
 OIDS | WITHOUT OIDS ]
    [ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
    [ TABLESPACE tablespace ]
    AS query

Description

CREATE TABLE AS creates a table and fills it with data computed by a SELECT command. The table columns have the names and data types associated with the output columns of the SELECT (except that you can override the column names by giving an explicit list of new column names).

CREATE TABLE AS bears some resemblance to creating a view, but it is really quite different: it creates a new table and evaluates the query just once to fill the new table initially. The new table will not track subsequent changes to the source tables of the query. In contrast, a view re-evaluates its defining SELECT statement whenever it is queried.

Parameters

GLOBAL or LOCAL: Ignored for compatibility. Refer to CREATE TABLE for details.

TEMPORARY or TEMP

If specified, the table is created as a temporary table. Refer to CREATE TABLE for details.

table_name

The name (optionally schema-qualified) of the table to be created.

column_name

The name of a column in the new table. If column names are not provided, they are taken from the output column names of the query. If the table is created from an EXECUTE command, a column name list cannot be specified.

WITH ( storage_parameter [= value] [, ... ] )

This clause specifies optional storage parameters for the new table; see Storage Parameters for more information. The WITH clause 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. See CREATE TABLE for more information.

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 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.

query

A SELECT or VALUES command, or an section 12.78 EXECUTE command that runs a prepared SELECT or VALUES query.

Notes

This command is functionally similar to SELECT INTO, but it is preferred since it is less likely to be confused with other uses of the SELECT INTO syntax. Furthermore, CREATE TABLE AS offers a superset of the functionality offered by SELECT INTO.

Prior to PostgreSQL 8.0, CREATE TABLE AS always included OIDs in the table it created. As of PostgreSQL 8.0, the CREATE TABLE AS command allows the user to explicitly specify whether OIDs should be included. If the presence of OIDs is not explicitly specified, the default_with_oids configuration variable is used. As of PostgreSQL 8.1, this variable is false by default, so the default behavior is not identical to pre-8.0 releases. Applications that require OIDs in the table created by CREATE TABLE AS should explicitly specify WITH (OIDS) to ensure proper behavior.

Examples

Create a new table films_recent consisting of only recent entries from the table films:

CREATE TABLE films_recent AS
  SELECT * FROM films WHERE date_prod >= '2002-01-01';

Create a new temporary table films_recent, consisting of only recent entries from the table films, using a prepared statement. The new table has OIDs and will be dropped at commit:

PREPARE recentfilms(date) AS
  SELECT * FROM films WHERE date_prod > $1;
CREATE TEMP TABLE films_recent WITH (OIDS) ON COMMIT DROP AS
  EXECUTE recentfilms('2002-01-01');

Compatibility

CREATE TABLE AS conforms to the SQL standard, with the following exceptions:

The standard requires parentheses around the subquery clause; in PostgreSQL, these parentheses are optional.
The standard defines a WITH [ NO ] DATA clause; this is not currently implemented by PostgreSQL. The behavior provided by PostgreSQL is equivalent to the standard's WITH DATA case. WITH NO DATA can be simulated by appending LIMIT 0 to the query.
PostgreSQL handles temporary tables in a way rather different from the standard; see CREATE TABLE for details.
The WITH clause is a PostgreSQL extension; neither storage parameters nor OIDs are in the standard.
The PostgreSQL concept of tablespaces is not part of the standard. Hence, the clause TABLESPACE is an extension.