SQL Server 2000: Why is this query w/ variables so slow vs w/o variables?

Posted by William DiStefano on Stack Overflow See other posts from Stack Overflow or by William DiStefano
Published on 2010-05-25T14:12:49Z Indexed on 2010/05/25 14:31 UTC
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I can't figure out why this query would be so slow with variables versus without them. I read some where that I need to enable "Dynamic Parameters" but I cannot find where to do this.

DECLARE
      @BeginDate AS DATETIME
     ,@EndDate AS DATETIME
SELECT
      @BeginDate = '2010-05-20'
     ,@EndDate = '2010-05-25'

-- Fix date range to include time values
SET @BeginDate = CONVERT(VARCHAR(10), ISNULL(@BeginDate, '01/01/1990'), 101) + ' 00:00'
SET @EndDate = CONVERT(VARCHAR(10), ISNULL(@EndDate, '12/31/2099'), 101) + ' 23:59'

SELECT
     *
FROM
    claim c
WHERE
    (c.Received_Date BETWEEN @BeginDate AND @EndDate) --this is much slower
    --(c.Received_Date BETWEEN '2010-05-20' AND '2010-05-25') --this is much faster

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