Select from one table where not in another

Question

I\'m trying to find the rows that are in one table but not another, both tables are in different databases and also have different column names on the column that I\'m using

Answer 1

You can LEFT JOIN the two tables. If there is no corresponding row in the second table, the values will be NULL.

SELECT id FROM partmaster LEFT JOIN product_details ON (...) WHERE product_details.part_num IS NULL