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Message Posted: Fri, 20 Feb 2004 @ 09:00:23 GMT
This is a pretty basic question, but I'm having trouble understanding it (please be kind J). Given the following information:
tbl1 has 2,500 rows tbl2 has 55,000,000 rows
the UPI for both tables is col1
Will these two SQL statements yield the same results?
sel a.c1,a.c2,a.c3 from tbl1 a left outer join tbl2 b on a.col1 = b.col1 and b.col1 is null; sel a.c1,a.c2,a.c3 from tbl1 a left outer join tbl2 b on a.col1 = b.col1 where b.col1 is null;
If not could you explain why not.
Doing an explain on both queries (stats have been collected), query 1 will take 7 + hours, and query 2 will take just over 2 minutes. By those results, I have a feeling that I may not get the same results I'm looking for.
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