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Topic

sqlfresher2k7
Aged Yak Warrior

623 Posts

Posted - 2011-12-01 : 11:08:33

How should i rewrite the below query to improve performance


delete from student
WHERE VALUE LIKE '%Open%'
and VALUE NOT LIKE '%;%;%'


delete from student
WHERE VALUE LIKE '%Close%'
and VALUE NOT LIKE '%;%;%;%'

russell
Pyro-ma-ni-yak

5072 Posts

Posted - 2011-12-01 : 11:35:35

If you really need leading wildcards, then you're not going to be able to optimize it.

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2011-12-01 : 11:39:33

quote:
Originally posted by sqlfresher2k7

How should i rewrite the below query to improve performance

delete from student
WHERE VALUE LIKE '%Open%'
and VALUE NOT LIKE '%;%;%'

delete from student
WHERE VALUE LIKE '%Close%'
and VALUE NOT LIKE '%;%;%;%'

is value storing delimited item list?

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

nigelrivett
Master Smack Fu Yak Hacker

3385 Posts

Posted - 2011-12-01 : 12:12:55

you could combine them

delete from student
WHERE VALUE NOT LIKE '%;%;%;%'
and (VALUE LIKE '%Close%' or VALUE LIKE '%Open%')

That will do a single table scan but you won't be able to get away from a scan of some sort.
You could put an index on VALUE so that it does an index scan maybe - might have to get the pk values (or unique clustered index values) and join to that for the delete.

==========================================
Cursors are useful if you don't know sql.
SSIS can be used in a similar way.
Beer is not cold and it isn't fizzy.

sqlfresher2k7
Aged Yak Warrior

623 Posts

Posted - 2011-12-01 : 16:32:46

Yes..the value storing delimited item list..

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2011-12-02 : 01:13:12

what are you trying to find using above conditions? are you trying to check cases where Open/Close values are coming and having total og less than 3/4 items?

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

sqlfresher2k7
Aged Yak Warrior

623 Posts

Posted - 2011-12-02 : 10:45:16

I am deleting the data with the condition specified..

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2011-12-02 : 10:47:07

quote:
Originally posted by sqlfresher2k7

I am deleting the data with the condition specified..

i'm asking what are the conditions? didnt understand meanings of like '%;%;%' etc

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

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