Join on nvarchar column using LIKE

• praveen_vejandla

  SSCrazy

  Points: 2069

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  January 22, 2013 at 12:49 am

  #393989

  UPDATE LII

  SET value_exists = 1

  FROM LII od

  JOIN VPL sl

  ON (sl.it like '%' + od.value + '%'

  AND od.opr = 9 )

  WHERE od.tn = 'VPL'

  AND od.cn = 'it'

  Is there anyway to rewrite above query for improved performance? I am joining two nvarchar columns (it, value) using LIKE and it seems very slow.

  Thanks.

• ChrisM@Work

  SSC Guru

  Points: 186127

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  January 22, 2013 at 12:59 am

  #1579465

  UPDATE od

  SET value_exists = 1

  FROM LII od

  INNER JOIN VPL sl

  ON sl.it LIKE '%' + od.value + '%'

  WHERE od.tn = 'VPL'

  AND od.cn = 'it'

  AND od.opr = 9

  The LIKE operator used with a wildcard on the left hand side of the search expression makes the join non-SARGable (Google it), which results in a table scan of table VPL. Do you really need the leading %?

  ^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

  For fast, accurate and documented assistance in answering your questions, please read this article.
  Understanding and using APPLY, (I) and (II) Paul White
  Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

• Bhuvnesh

  SSC Guru

  Points: 59351

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  January 22, 2013 at 1:05 am

  #1579467

  praveen_vejandla (1/22/2013)

  ---

  UPDATE LII

  SET value_exists = 1

  FROM LII od

  JOIN VPL sl

  ON (sl.it like '%' + od.value + '%'

  AND od.opr = 9 )

  WHERE od.tn = 'VPL'

  AND od.cn = 'it'

  Is there anyway to rewrite above query for improved performance? I am joining two nvarchar columns (it, value) using LIKE and it seems very slow.

  Thanks.

  send the index deifnition of Lil and VPL table

  -------Bhuvnesh----------
  I work only to learn Sql Server...though my company pays me for getting their stuff done;-)