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
