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