The truncate TABLE statement is a powerful tool used to delete all records from a table in Oracle. It performs the same function as a DELETE statement without a WHERE clause, and is much faster and more efficient. Once a table is truncated, it cannot be reversed. But does the TRUNCATE TABLE statement affect any of the table's indexes, triggers, or dependencies? In Oracle, the truncate statement is used to delete all records in a table, while keeping the table structure intact.
If the table is split, all partitions or subpartitions, as well as the LOB and LOB index data segments for each partition or subpartition, are truncated. When you truncate a cluster, the database also automatically deletes all data from the indexes of the cluster tables. The TRUNCATE TABLE CASCADE statement is used to delete all rows from the table and also to truncate all associated tables. This is a recursive operation that will truncate all child tables, granchild tables, etc., using the specified options.
Oracle Database also sets the NEXT storage parameter to the size of the last extent removed from the segment in the truncation process. If a regular or index-organized table contains LOB columns, all LOB data and LOB index segments are truncated. The STORAGE clause allows you to choose between deleting or reusing the storage freed by the truncated rows and the associated indexes, if any. Deleting rows with the TRUNCATE statement can be faster than deleting all rows with the DELETE statement, especially if the table has many triggers, indexes, and other dependencies. It is important to note that the TRUNCATE TABLE CASCADE statement requires foreign key constraints defined with the ON DELETE CASCADE clause to work. In conclusion, Oracle's TRUNCATE statement is an incredibly useful tool for quickly and efficiently deleting all records from a table.
It works just like a DELETE statement but without using a WHERE clause, and it does not generate rollback data. It can also be more efficient than deleting and re-creating a table.