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SQL Exists function help

Posted on 2007-11-30
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Last Modified: 2012-08-14
Why does code 1 below give different results than code 2? Which one should I trust?

CODE 1
SELECT   * FROM   [User]
WHERE   NOT EXISTS (SELECT     userid FROM [user_location])
GIVES NO RESULTS

CODE 2
SELECT   * FROM   [User]
WHERE   UserId NOT IN (SELECT  userid FROM [user_location])
GIVES SOME RESULTS
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Question by:mattphung
7 Comments
 
LVL 75

Accepted Solution

by:
Aneesh Retnakaran earned 500 total points
ID: 20383303
Hello mattphung,

Code 2  or this one

SELECT   * FROM   [User] u
WHERE   NOT EXISTS (SELECT     userid FROM [user_location] ul where u.userID = ul.UserID )



Aneesh R
0
 
LVL 17

Expert Comment

by:Shanmuga Sundaram
ID: 20383314
only this syntax is correct

SELECT   * FROM   [User]
WHERE   UserId NOT IN (SELECT  userid FROM [user_location])
0
 
LVL 6

Expert Comment

by:messen1975
ID: 20383316
I'd expect Code 1 to return no results
and
Code 2 to return all rows where the UserID is not in user_location
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LVL 17

Expert Comment

by:Shanmuga Sundaram
ID: 20383320
For this
SELECT   * FROM   [User]
WHERE  (Which field you are checking is missing here )  NOT EXISTS (SELECT     userid FROM [user_location])
GIVES NO RESULTS
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LVL 6

Expert Comment

by:messen1975
ID: 20383338
I'd right that (Assuming you want all Users Not in user_location) as


Select * 
From User left Join User_Location on user.UserID = user_location.userid
Where user_location.userid is null

Open in new window

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LVL 47

Expert Comment

by:Vitor Montalvão
ID: 20383348
Code 1 doesn't return results because it's incomplete. Need to join user_location to user, like aneeshattingal wrote. So you should trust Code 2.
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Author Comment

by:mattphung
ID: 20383368
shasunder:
 Your code gave a syntax error.  Thanks anywhere.

aneeshattingal: solution was the best one
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