Question

I have been doing some searching but have not been able to find an answer for this so thought I would ask here as the people here know everything 🙂

I am trying to combine these 2 update queries into one query.

UPDATE addresses SET is_default='0' WHERE id!='1'
UPDATE addresses SET is_default='1' WHERE id='1'

I assume this should be too hard to accomplish but i cant seem to work it out 🙁

Thanks

Paul

Answer 1

You can use CASE to do this:

UPDATE addresses SET is_default = CASE WHEN id = 1 THEN 1 ELSE 0 END;

In your example, you’re updating the entire table, so you wouldn’t benefit from indexes no matter what, but if you were only doing a subset of values, you’d still want to leave the where in (because its very doubtful the optimizer could figure out how to use the index). For example:

UPDATE foo
  SET
    bar = CASE id WHEN 1 THEN 1 WHEN 2 THEN 0 ELSE bar END
    baz = CASE WHEN id = 3 THEN 7 ELSE baz END
  WHERE id IN (1,2,3)

(Note the two different CASE syntaxes).