Bob Hovious 24601 (9/23/2009)
update table1
set val=a2.val
from table2 a2
where table1.id = a2.id
Hey Bob... Jeff has posted about this type of update before. Basically, it's a time bomb waiting to explode, and when it does it will cause extreme slowness in your server.
The first table in the from clause should always be the target table. Therefore, the correct way to write this is:
update table1
set val=a2.val
from table1, table2 a2
where table1.id = a2.id
Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes