compare differences between two tables in mysql

Question

Same as oracle diff: how to compare two tables? except in mysql.

Suppose I have two tables, t1 and t2 which are identical in layout but which may contain

Answer 1

 select t1.user_id,t2.user_id 
 from t1 left join t2 ON t1.user_id = t2.user_id 
 and t1.username=t2.username 
 and t1.first_name=t2.first_name 
 and t1.last_name=t2.last_name

try this. This will compare your table and find all matching pairs, if any mismatch return NULL on left.