Post reply

Select query taking more times

  • February 7, 2012 at 5:38 am

    #256365

    I am a DBA, my quy gave one query to execute , i have run that query it taken 54 seconds, then i anay clustered index scan 46% ? what is meaning ?

    Thanks

  • February 7, 2012 at 5:39 am

    #1443700

    If you're talking about the execution plan, it means that the query optimiser estimated that the clustered index scan (which is a read of the entire table) was 46% of the cost of the entire query.

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

  • February 7, 2012 at 6:02 am

    #1443715

    ok. How to find performance slow down in query.

  • February 7, 2012 at 6:21 am

    #1443724

    That specific query or any query?

    If that specific query, post it here with exec plan, table and index definitions and someone will take a look. If any query in general, then maybe get hold of this: http://www.amazon.com/Server-Query-Performance-Tuning-Distilled/dp/1430219025/ref=sr_1_1?ie=UTF8&s=books&qid=1237206053&sr=8-1

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

  • February 7, 2012 at 6:49 am

    #1443735

    If it's scanning the index, it can mean you're returning so much data that it has not choice but to scan. Or, it could mean that the index isn't very selective. Or, it could mean that you have functions in your WHERE or JOIN criteria on the column which forces a scan. Or... In short, there are lots of causes, so it's really hard to tell you what the problem is without more detail.

    "The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
    - Theodore Roosevelt

    Author of:
    SQL Server Execution Plans
    SQL Server Query Performance Tuning

  • February 7, 2012 at 7:06 am

    #1443749

    Total records: 8500, They are used one view , more joins also in that query.. I checked Exection plan. it showing , Clustered Index scan 65% and Hash Join 8% ... thick lines,

  • February 7, 2012 at 7:10 am

    #1443752

    Cool.

    So with Grant's list you have somewhere to start investigating. Post back with more info if you need more help.

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

Viewing 7 posts - 1 through 6 (of 6 total)

You must be logged in to reply to this topic. Login to reply