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Speed up delete with SQL Server

Posted on 2002-05-28
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Last Modified: 2007-12-19
I have to delete rows on a table that has about 200 000 rows WHERE usager = "XXXXX" .  There are 2 non-clustered indexes on this table but SQL Server doesn't always use, it depends on how many rows there is to delete.  The delete execution takes over 3 minutes!!!  How can I speed that up?
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Question by:Flower11
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8 Comments
 
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by:Guy Hengel [angelIII / a3]
ID: 7041084
If you add/modify a clustered index on the usager column, you will probably get a better deletion time.
CHeers
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by:kelfink
ID: 7042800
If sql server is making the choice depending on the count, then it sounds like it's probably making good decisions based on the count.  

If this table is the parent of foreign keys, then remember that it must guarrantee that child records don't exist, or it would have to throw an error.

Could it be referring to huge tables?  For instance,
a "small" table might be the products in a store, where a larger table would be the orders in the store.  If you delete a product, sql server would check the orders table to make sure no orphan records would be left behind.  Make certain that any reference to the target table (in this case, product) in the child table (orders) requires a table scan.  

If your child table has column 'prod_id' referring to 'id' in the prod table, make sure 'prod_id' is indexed, or sql server must table-scan the child table for each record being deleted from the parent.
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by:Flower11
ID: 7044546
Thanks angellll.

But a clustered index has to be unique, doesn't it?  There is many rows with the same "usager".
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Author Comment

by:Flower11
ID: 7044553
Answer to kelfink.

The table is temporary, and there is no foreign key.

Flower11
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by:Guy Hengel [angelIII / a3]
ID: 7044561
The clustered index doesn't need to be on a single column, and doesnt event need to be unique at all...

CHeers
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by:thegroup
ID: 7044674
If your table doesn't reference another one try building an index on your search field (usager)

Disabling indexes allows you to execute the delete very fast, then you reenable the index to rebuild it.

I don't know SQL Server very well, but in Interbase the sintaxis is:

alter index <index> inactive;
<do your stuff>
alter index <index> active;

Hope helps.
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by:nico5038
ID: 7265834

No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:
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Please leave any comments here within the
next seven days.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER !

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