How to find the difference between two tables?

Question

I have a MySQL database ver 5.1. I have two tables Table_A will always keep the records in it. Table_B will be used to only compare the differences. Is there a MySQL query function via PHP that will compare the rows and tell me what rows are missing on Table_B .

Table_A

user    name
 1      bob
 1      joe
 1      sally
 1      matt

Table_B

user    name
 1      bob
 1      joe
 1      sally
 1      john

When the PHP query was run how would I compare Table_A vs Table_B ? All I need is to tell me that matt no longer exists and it will add john to Table_A .

What would be the best way to do this?

Thanks.

Answer 1

SELECT name FROM Table_A WHERE name NOT IN (SELECT name FROM Table_B)