Showing posts with label rewrite. Show all posts
Showing posts with label rewrite. Show all posts

Friday, March 9, 2012

Query Optimization

IS there any way to rewrite this Query in optimized way?

SELECT dbo.Table1.EmpId E from dbo.Table1
where EmpId in(
SELECT dbo.Table1.EmpId
FROM (SELECT DISTINCT PersonID, MAX(dtmStatusDate) AS dtmStatusDate
FROM dbo.Table1
GROUP BY PersonID) derived_table INNER JOIN
dbo.Table1 ON derived_table.PersonID = dbo.Table1.PersonID AND
derived_table.dtmStatusDate = dbo.Table1.dtmStatusDate))

Thanks...jDon't know abiut being faster but I think this is what oyu are trying to do. (get the empid's with max(dtmStatusDate) from each person.

SELECT t1.EmpId
from dbo.Table1 t1
where t1.dtmStatusDate =
(select max(dtmStatusDate) from dbo.Table1 t2 where t1.PersonID = t2.PersonID)

also try

SELECT t1.EmpId
from dbo.Table1 t1
where not exists ( select * from dbo.Table1 t2 where t1.PersonID = t2.PersonID and t1.dtmStatusDate < t2.dtmStatusDate)