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This article introduces the relevant knowledge of "what is the execution order of where clauses". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Look at the code:

The copy code is as follows:

Set statistics io on

Set statistics time on

Go

Set statistics profile on

Go

Use pubs

Select * from authors

Where (au_fname like's%'or au_fname like'a%')

And (state like 'CA' or state like' UT')

And (cast (zip as int) > 90000)

Select * from authors

Where (au_fname like's%'or au_fname like'a%')

And (cast (zip as int) > 90000)

And (state like 'CA' or state like' UT')

Select * from authors

Where (cast (zip as int) > 90000)

And (au_fname like's%'or au_fname like'a%')

And (state like 'CA' or state like' UT')

Purpose: to verify the query order of each condition of the where statement

Environment: SQLServer 2005Express version

Step: display the query plan

The result: without exception, all are unified into this kind of code.

The copy code is as follows:

|-- Clustered Index Scan (OBJECT: ([pubs]. [DBO] .[ auidind] .UPKCL _ auidind]), WHERE: (CONVERT (int, [pubs]. [DBO]. [zip]. 0) > (90000) AND ([pubs] .[ dbo] .[ pubs] .[ au _ fname] like's%'OR [pubs] .[ au _ fname] like'a%') AND ([pubs]. [DBO] .[ state] like 'CA' OR [pubs] .[ state] like' UT')

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