Tuesday, August 18, 2009

FULL OUTER JOIN

背景
改完某個page，發現load個page時慢到嚇死人，睇返個logic，個bottleneck係有條stored proc行得好慢

邪惡的FULL OUTER JOIN
原來條stored proc入面的query用了FULL OUTER JOIN

Solution
因應情況而嘗試改用UNION ALL，結果係execution plan經已看到，而execution time亦由50s 減到1s

結論：FULL OUTER JOIN 真的很邪惡
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1 comment:

Unknown said...

Practically I can't figure out a case that "FULL OUTER JOIN" can be utilized... Is it really a case that MUST/SHOULD use it by the way?

August 21, 2009 at 1:23 PM

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