Temporary Table in PostgreSQL

Patrycja Dybka

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Dec 29, 2014

CPOL

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Temporary table is a special table that is bound to a transaction or to a session. It means that the data in the temporary table and the definition lasts till the end of the transaction or session.

How to Create a Temporary Table

The syntax to create a temporary table is as provided below:

Creating a temporary table transaction-specific, where all rows are deleted on COMMIT.

 CREATE [ GLOBAL|LOCAL ] {TEMPORARY | TEMP } TABLE table_name
 ( column_name data_type, 
               ... 
                        ... 
                                  ... ) ON COMMIT DELETE ROWS;

Creating a temporary table transaction-specific, where table is dropped on COMMIT.

CREATE [ GLOBAL|LOCAL ] {TEMPORARY | TEMP } TABLE table_name
 ( column_name data_type, 
               ... 
                        ... 
                                  ... ) ON COMMIT DROP;

Creating a temporary table session-specific.

CREATE [ GLOBAL|LOCAL ] {TEMPORARY | TEMP } TABLE table_name
 ( column_name data_type, 
               ... 
                        ... 
                                  ... ) ON COMMIT PRESERVE ROWS;

Note:

In order to create a temporary table, you can use alternately TEMPORARY and TEMP.
GLOBAL and LOCAL keywords may be used optionally. They are depreciated and don't make any differences in PostgreSQL.

Some Examples of Usage

may be used to convey data among triggers for either session or a transaction
to store temporarily data for arithmetic

Differences between Temporary Tables in PostgreSQL and Oracle

	PostgreSQL	Oracle	Comment
Syntax	CREATE [ GLOBAL\|LOCAL ] {TEMPORARY \| TEMP} TABLE table_name ( column_name data_type, … … … )[ ON COMMIT {DELETE ROWS\|PRESERVE ROWS\|DROP }];	CREATE GLOBAL TEMPORARY TABLE table_name ( column_name data_type, … … … )[ON COMMIT {DELETE ROWS \| PRESERVE ROWS}]	In Oracle, `GLOBAL` keyword must be specified. Oracle doesn't support `ON COMMIT DROP`.

Visibility	Both table definition and data are visible to the current session	The data in temporary table is private to each session. The definition of temporary table is visible to all sessions.

Definition of temporary table	The definition isn't stored permanently. Each session must create it.	The definition is stored permanently.	PostgreSQL doesn't have very important feature that Oracle has: The definiton of temporary table remains after end of session. It's not necessary to perform many DDL operations. These operations shouldn't be a part of the system and should be used only in case to rebuild it.

Default	`ON COMMIT PRESERVE ROWS` is default in PostgreSQL	`ON COMMIT DELETE ROWS` is default in Oracle

Related reading about Oracle Global Temporary Table: Highlights of the Oracle database: Global Temporary Table