EXPERT RESPONSE
The best answer is: it depends.
It depends on which database system you're using.
It depends on how sophisticated the optimizer is.
It depends on which indexes you have defined on the columns.
It depends on how complex the query is.
It depends on whether the current month name has an R in it.
Okay, I was kidding about that last one.
Here are two interesting articles that touch this issue
in slightly more detail than I would:
The final answer? You will have to run performance tests on your
own tables with your own subqueries and joins, and compare the results.
That was my advice in
NOT EXISTS correlated subquery, or OUTER JOIN? (20 September 2004).
That said, my preference is often for the subquery. A subquery just
seems to convey the semantics of what the query is trying to achieve
better than a join. For an example, see my previous answer
Subquery or join? (20 October 2003).
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