2
in the case you describe, EXISTS is not required.
in other cases, EXISTS is not placed as you do it, more like:
UPDATE products SET status=0 WHERE EXISTS...
but it's mainly used in conjunction with subqueries, which MySQL supports very very badly...
In your example, leaving out the EXISTS will still get the job done - if products_id=2731 doesn't exist, the query will fail or at least return a getRowsNum = 0 - leaving the "EXISTS" clause effectless
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