Using LIMIT 1 in MySQL

Question

When is it appropriate to add LIMIT 1 at the end of the query in MySQL. I normally add it in DELETE but I\'ve seen it being used with INSERT a and even UPDATE. Is it an overkill

Answer 1

Assume you are writing Forgot Password code (in PHP):

UPDATE
    `users`
SET
    `pass` = PASSWORD('{$new_salted_pass}')
WHERE
    `account_id` = '{$account_id}'
LIMIT 1

If your software is a Software as a Service (SaaS),

and multiple organizations use your software,

and account_id-organization_id fields together are a unique id,

and the account_id is auto-generated in the code like so:

JONES0001
JONES0002
JONES0003
...

and the software engineer forgets to add AND organization_id = '{$organization_id}' to the query's WHERE condition,

and the code passes QA when testing the Forgot Password functionality in QA environment,

and the code is then pushed to production,

then the LIMIT 1 can limit the damage done when two organizations' user's share the same account_id.