SQL Gotchas
I think you can imagine the amount of paint involved in having a query behave in an unexpected manner. I have run into both of those recently. This one had me doubting my sanity (imagine this on a table with several hundred thousands records, with a fairly complex query around it:
select 1
where 1 not in (2,3,null)
select 1 where 'e' = 'e '

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