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Re: How to create a before update trigger for 2 fields "expected_hash" and "identify_hash" (both allow null)
Posted by: Peter Brawley
Date: July 02, 2021 07:51AM



- While `expected_hash` is NULL, `identify_hash` may also be NULL ("nullable").

- while `expected_hash` is NOT NULL, `identify_hash` may be NULL
--> While `expected_hash` is NULL, `identify_hash` must NOT be non-NULL

- While `expected_hash` AND `identify_hash` is NOT NULL, `identify_hash` must == `expected_hash`.

What's unclear to you---how to turn those requirements into an IF...ELSE...END IF sequence referencing old old.expected_hash and old_identity_hash?

Read the manual pages on Triggers and on IF...ELSE...END IF, then give it a try. If you get stuck, post what you have here.

Edited 1 time(s). Last edit at 07/02/2021 08:10AM by Peter Brawley.

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