Wednesday, November 19, 2008

difference between Truncate and Delete interms of Referential Integrity

What is the difference between Truncate and Delete interms of Referential Integrity?

DELETE removes one or more records in a table, checking referential Constraints (to see if there are dependent child records) and firing any DELETE triggers. In the order you are deleting (child first then parent) There will be no problems. TRUNCATE removes ALL records in a table. It does not execute any triggers. Also, it only checks for the existence (and status) of another foreign key Pointing to the table. If one exists and is enabled, then you will get The following error. This is true even if you do the child tables first. ORA-02266: unique/primary keys in table referenced by enabled foreign keys You should disable the foreign key constraints in the child tables before issuing the TRUNCATE command, then re-enable them afterwards.

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