Updating 4 million Records - SQL Server Forums

Please start any new threads on our new site at https://forums.sqlteam.com. We've got lots of great SQL Server experts to answer whatever question you can come up with.

All Forums

General SQL Server Forums

New to SQL Server Programming

Updating 4 million Records

Author

Topic

AskSQLTeam
Ask SQLTeam Question

0 Posts

Posted - 2006-08-30 : 10:47:23

Meg writes "Hi,

I have a table that has 4+ million records. I need to update those records. I am facing some performance issue. Can someone please advice?

update stage
set batch_status = 1
where update_status = 0

Update transaction
Set aId = s.aId,
b = s.b,

from stage s
Where s.aId = transaction.aId
and s.batch_status = 1

Update stage
Set update_status = 1,
batch_status = 2

where

batch_status = 1

When I run the above query with "set rowcount 1000", it runs in one minute. When I run the query for "set rowcount 10000", it runs in 1 hour 56 minutes. Can someone help me to optimize it?

Thanks.
Meg"

nr
SQLTeam MVY

12543 Posts

Posted - 2006-08-30 : 10:51:06

WHat indexes do you have on the tables.
Try
stage batch_status, aId

and
transaction aId

also the second update should be

Update transaction
Set b = s.b,
from stage s
Where s.aId = transaction.aId
and s.batch_status = 1

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

blindman
Master Smack Fu Yak Hacker

2365 Posts

Posted - 2006-08-30 : 11:26:39

If batch_status is boolean then indexing it may not help. As a matter of fact, she might be better off temporarily removing some of the indexes from the table.

Meg, give us a list of the indexes on the tables, as nr suggested.

Also, try running the script for 1000 records through Query Analyzer and check out the execution plan. What does it say is taking up the majority of the time?

nr
SQLTeam MVY

12543 Posts

Posted - 2006-08-30 : 11:42:12

Even if batch status is a boolean it will still help as long as the search is on the value with the smailler number of rows.

I assume the rowcount is used for the set of this value in the first query.

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

blindman
Master Smack Fu Yak Hacker

2365 Posts

Posted - 2006-08-30 : 16:04:49

In my testing, a BIT value always resulted in an index scan, regardless of cardinality.
When the boolean value was represented in a smallint column an index seek was always used, regardless of cardinality.
So it may depend upon the datatype. Perhaps the server always performs scans on BIT data columns.

Subscribe to SQLTeam.com

SQLTeam.com Articles via RSS

SQLTeam.com Weblog via RSS

- Advertisement -

Resources