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SQL Server 2000 General discussion of Microsoft SQL Server -- for topics that don't fit in one of the more specific SQL Server forums. version 2000 only. There's a new forum for SQL Server 2005.
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Old August 14th, 2003, 09:17 PM
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Default performance of sql statement

Which SQL statement is better in performance?
1. select * from emp e, dept d
   where e.dept_id=d.dept_id
   and d.dept_name='ACCOUNT'

2. select * from emp e, dept d
   where d.dept_name='ACCOUNT'
   and e.dept_id=d.dept_id



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Old August 15th, 2003, 06:00 AM
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I don't think you will see any difference between these two queries. Generally speaking, the optimizer will evaluate WHERE predicates in whatever order it chooses, and in whatever order it thinks best. Even though one of the predicates is actually an old style, deprecated form of specifying a JOIN, and the other is a row selection, depending upon the presence of indexes and the distribution of data values these most likely will be processed in 'parallel', that is, more or less at the same time, while the JOIN results are being built.

You can inspect the query execution plan on your database to see if there is any difference between the two. My guess is that they will be identical.

Jeff Mason
Custom Apps, Inc.
www.custom-apps.com
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