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SQL Select where doesnt (not) exist in another table?

Posted on 2009-04-25
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Last Modified: 2012-05-06
Another SQL question for you experts.

I have 2 tables:
tblContacts (ID, Name, etc)
tblContactGroupMapping(contactID, groupID)

I want to write a query that will select all the Contacts who are not assigned to at least 1 group in the tblContactGroupMapping table.

It seems like it should be easy with set operations, but i've never used those in SQL... or is there a better way?
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Question by:BobBarker_99
4 Comments
 
LVL 25

Accepted Solution

by:
reb73 earned 1600 total points
ID: 24232639
Try -
Select c.*
from tblContacts c
where not exists (select null from tblcontactgroupmapping where contactid = c.id)

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LVL 41

Assisted Solution

by:ralmada
ralmada earned 200 total points
ID: 24232754
Another alternative is using left join. Please check this out.

select a.* from tblContacts a
left join tblContactGroupMapping b on a.ID = b.contactID
where b.groupID is null

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Assisted Solution

by:MeghanOBrien
MeghanOBrien earned 200 total points
ID: 24233206


select * 
from tblContacts
where not exists (select * 
					from tblContactGroupMapping
					where tblContactGroupMapping.ContactID = tblContacts.ID)

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Author Closing Comment

by:BobBarker_99
ID: 31574532
THanks.  THey all work great, and taught me a little more about sql.  
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