Question

I have 2 tables with same structures.

current_db = 521,892 rows and primary key is email

new_db = 575,992 rows and primary key is email

On new_db I want delete existing email address which already in current_db.

Question :

How do I compare & delete existing email on new_db and the results on new_db only be 54,100

Answer 1

Check the rows you want to delete –

SELECT n.* FROM new_db n
  JOIN current_db c
    ON n.email = c.email;

Delete them –

DELETE n
FROM new_db n
  JOIN current_db c
    ON n.email = c.email;