DELETE DATE_ADD Mysql query how to write correctly?

Question

MySQL

I need to make sure that messages that come in the form msg are deleted after 30 minutes from the last message sent, d is DATETIME.
mysql_query("DELETE FROM msg WHERE d <= DATE_ADD(d,INTERVAL -30 MINUTE)"); // Tried something x(
Thanks for the help!

Answer 1

DELETE FROM msg WHERE d <= DATE_ADD(SELECT MAX(d) FROM msg,INTERVAL -30 MINUTE)

try like this