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The third performs an update, and conditionally inserts the row if the update touches zero rows.The fourth inserts the row, then performs an update if the insert fails with a duplicate value on index exception.The data in a global temporary table is private, such that data inserted by a session can only be accessed by that session.The session-specific rows in a global temporary table can be preserved for the whole session, or just for the current transaction.
INSERT INTO my_temp_table VALUES (1, 'ONE'); SELECT COUNT(*) FROM my_temp_table; COUNT(*) ---------- 1 SQL CREATE GLOBAL TEMPORARY TABLE my_temp_table ( id NUMBER, description VARCHAR2(20) ) ON COMMIT PRESERVE ROWS; -- Insert and commit, then check contents of GTT.
Unfortunately, prior to Oracle 12c, all undo associated with DML against a GTT is written to the normal undo tablespace, which is itself protected by redo.
As a result, using a GTT reduces the amount of redo generation, but does not eliminate it.
INSERT INTO my_temp_table WITH data AS ( SELECT 1 AS id FROM dual CONNECT BY level If you've read the previous section, you will already know the relationship between global temporary tables and redo.
The data in a GTT is written to the temporary tablespace, which is not directly protected by redo, so using a GTT improves performance by reducing redo generation.
tablespace_name, s.extent_management FROM user_tables t, user_tablespaces s WHERE t.tablespace_name = s.