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Was it always a million records? Was it was tested against files with only a few records? Prior runs over small files can convince SQL that using the index will slow down the access compared to a table scan.
Paul
Principal Programmer Analyst
IS Supply Chain/Replenishment
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of franz400@xxxxxxxxxxxx
Sent: Monday, August 30, 2010 2:33 PM
To: midrange-l@xxxxxxxxxxxx
Subject: sql join performance issue
Reviewing a performance issue, .net app opening a cursor that has sql selects that are inserted into a temp table. Two large orders files (FILEA & FILEB) and a temp file (FILEC) with the single record of the Cust and Region selected.
FILEA inner join FILEB on aORDER = bORDER inner join FILEC on aCUST = cCUST,aREGION = cREGION
Visual Explain is saying FILEB is a table scan even though it has an index of ORDER (there is 1 rec per order in "a" and also "b").
Not understanding why it needed a table scan of a million recs to get 80 records for a cust/region
Jim Franz
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