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Oracle performance issue with "UNION ALL" in 10g
Hi,
just assume that
SQL Query :
SQL1 UNION ALL SQL2
separately exection times are
SQL1 -- 5 seconds (total count - 5,00000)
SQL2 -- 10 seconds (total count - 4,00000)
if I use UNION ALL. it takes 30 minutes to complete the execution.why it takes that much time if I use UNION ALL.?
Thanks
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look at what, you haven;t posted anything to look at
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is therey anyway to improve performance of that query ? if we use UNION ALL it takes much time. do we need to use any hints or any other function?
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what query, you havent posted anything
no query
no execution plan
no anything
posting stuff in different colours doesnt make it less true
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Originally Posted by victoryhendry
Hi,
just assume that
SQL Query :
SQL1 UNION ALL SQL2
separately exection times are
SQL1 -- 5 seconds (total count - 5,00000)
SQL2 -- 10 seconds (total count - 4,00000)
if I use UNION ALL. it takes 30 minutes to complete the execution.why it takes that much time if I use UNION ALL.?
Thanks
Trace the three executions, compare execution plans as well as buffer_gets.
Pablo (Paul) Berzukov
Author of Understanding Database Administration available at amazon and other bookstores.
Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.
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