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Tunning of SQL query

Posted on 2004-08-13
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Last Modified: 2008-03-17
I have a table which have more than 4m (4,000,000) records.
When i query as
SELECT * FROM TBL_RECORD WHERE NAME = 'test', it takes 2 seconds.
When i use like it takes 4 seconds.
SELECT * FROM TBL_RECORD WHERE NAME like '%test%'

I want to use the like condition in a stored procedure, but can anyone please let me what other statement can i add to faster the query.
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Question by:saroopchand
5 Comments
 
LVL 17

Accepted Solution

by:
BillAn1 earned 25 total points
ID: 11796403
unfortunately the like '%test%' will slow things down a lot.
If you dont need it, you might want to remove the leading % - like 'test%' will be a much quicker.
The problem is that with a LIKE comparison, it cannot use an index, and it has to scan through the whole text of each field. If you use like 'test%' it at least only has to match the start of the string.
What is your dat like? could you normalise it? If there are only a small (say 1000's ) of distinct values of text, you could put the text into a small table with an integer key, then link this table your data. Then the LIKE only has to be done on much less # of records, and the main fact table can be scanned on an integer index. Much quicker.
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Assisted Solution

by:Lowfatspread
Lowfatspread earned 25 total points
ID: 11796835
as BillAn1 has replied,

the only other aspect to consider is do you need all the columns returned? (less should be quicker)

could you go Case INSENSITIVE (Should be Faster , at expense of Disk space)

If you dont want all columns returned , a covering index of the columns you want plus the name  column
may be faster... (again at the expense of disk on Maintenance I/O)

what is the Data Type of NAME ?

Charindex/Patindex can sometimes be faster

hth



 
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LVL 42

Expert Comment

by:EugeneZ
ID: 11797529
create index  on NAME field - if you have not yet
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