difference between where and nested queries
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by Chris H
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Published on 2010-04-15T23:21:23Z
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2010/04/15
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sql
I'm not able to figure out the difference between these queries. I'm pretty sure that the first one is an equi-join. I'm not sure how the second one ISN'T the same as the first. The sub query in #2 selects all Ids from S, and then it returns all R's that also have those ID's, no?
SELECT R.cname FROM R, S, WHERE R.Id = S.Id
SELECT R.cname FROM R WHERE R.Id IN (SELECT S.Id FROM S)
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