A must-know about NOT IN in SQL – more antijoin optimization
I will try to make it short and clear: if you are writing SQL queries with “NOT IN” like
SELECT … WHERE x NOT IN (SELECT y FROM …)
you have to be sure to first understand what happens when “x” or “y” are NULL: it might not be what you want!…
Source: A must-know about NOT IN in SQL – more antijoin optimization
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