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How to exclude rows that don’t join with another table?

I have two tables, one has primary key other has it as a foreign key.

I want to pull data from the primary table, only if the secondary table does not have an entry containing it’s key. Sort of an opposite of a simple inner join, which returns only rows that join together by that key.

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Answer

alt text

SELECT <select_list> 
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL

Full image of join alt text

From aticle : http://www.codeproject.com/KB/database/Visual_SQL_Joins.aspx

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