Oracle performance issue with "UNION ALL" in 10g
DBAsupport.com Forums - Powered by vBulletin
Results 1 to 6 of 6

Thread: Oracle performance issue with "UNION ALL" in 10g

Hybrid View

  1. #1
    Join Date
    Sep 2010
    Posts
    3

    Exclamation 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

  2. #2
    Join Date
    Sep 2010
    Posts
    3
    could you pls look on it

  3. #3
    Join Date
    Sep 2002
    Location
    England
    Posts
    7,333
    look at what, you haven;t posted anything to look at

  4. #4
    Join Date
    Sep 2010
    Posts
    3
    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?

  5. #5
    Join Date
    Sep 2002
    Location
    England
    Posts
    7,333
    what query, you havent posted anything
    no query
    no execution plan
    no anything

    posting stuff in different colours doesnt make it less true

  6. #6
    Join Date
    Mar 2007
    Location
    Ft. Lauderdale, FL
    Posts
    3,554
    Quote Originally Posted by victoryhendry View Post
    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.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Click Here to Expand Forum to Full Width