Temporary tables are stored in the temporary file. Pages from the temporary file can be cached, just as pages from any other dbspace can. Operations on temporary tables are never written to the transaction log. There are two types of temporary tables: local temporary tables and global temporary tables.
A local temporary table exists only for the duration of a connection or, if defined inside a compound statement, for the duration of the compound statement.
A global temporary table remains in the database until explicitly removed using a DROP TABLE statement. The term global is used to indicate that multiple connections from the same or different applications can use the table at the same time. The characteristics of global temporary tables are as follows:
There are two types of global temporary tables: non-shared and shared. Normally, a global temporary table is non-shared; that is, each connection sees only its own rows in the table. When a connection ends, rows for that connection are deleted from the table.
When a global temporary table is shared, all of the table's data is shared across all connections. To create a shared global temporary table, you specify the SHARE BY ALL clause at table creation. In addition to the general characteristics for global temporary tables, the following characteristics apply to shared global temporary tables:
Temporary tables can be declared as non-transactional using the NOT TRANSACTIONAL clause of the CREATE TABLE statement. The NOT TRANSACTIONAL clause provides performance improvements in some circumstances because operations on non-transactional temporary tables do not cause entries to be made in the rollback log. For example, NOT TRANSACTIONAL may be useful if procedures that use the temporary table are called repeatedly with no intervening COMMIT or ROLLBACK, or if the table contains many rows. Changes to non-transactional temporary tables are not affected by COMMIT or ROLLBACK
|Send feedback about this page via email or DocCommentXchange||Copyright © 2008, iAnywhere Solutions, Inc. - SQL Anywhere 11.0.0|