confermo ed aggiungo:

http://dev.mysql.com/doc/mysql/en/JOIN.html

You want to select all rows from table1 which don't exist in table 2?
Example:
table1.id = list(1, 2, 3, 4, 5)
table2.id = list(1, 2, 5)
You want to have 3 and 4 as the result cause they are not in table 2?
Use the OUTER JOIN:
SELECT table1.* FROM table1 LEFT JOIN table2 ON table1.id=table2.id WHERE table2.id IS NULL