Question

TableA :
ID,
mail,
team,
[other columns]

TableB :
ID,
mail,
team,
[other columns]

ID is the primary key in both tables. I need to work through every row in TableB and :

1. If ID doesn’t exist in TableA, insert new row – using columns
   ID,mail,team (only)
2. If ID does exist in TableA, update row with new value for mail (only)
3. ID’s that exist in TableA but not TableB row should
   remain unchanged

I have :

INSERT INTO tablea (id,mail,team) (SELECT id,mail,team FROM tableb)
ON DUPLICATE KEY update tablea SET tablea.mail=tableb.mail;

This doesn’t work – I think I need a join to make the last SET command valid, but not sure on this part, can anyone help?

Many Thanks

Answer 1

As documented under INSERT ... ON DUPLICATE KEY UPDATE Syntax:

You can use the VALUES(col_name) function in the UPDATE clause to refer to column values from the INSERT portion of the INSERT ... ON DUPLICATE KEY UPDATE statement. In other words, VALUES(col_name) in the ON DUPLICATE KEY UPDATE clause refers to the value of col_name that would be inserted, had no duplicate-key conflict occurred. This function is especially useful in multiple-row inserts.

Therefore:

INSERT INTO tablea (id, mail, team)
SELECT id, mail, team FROM tableb
ON DUPLICATE KEY UPDATE mail = VALUES(mail)