MySQL INSERT on condition

Question

我有一个表user_has_alerts (userID, alertID, datealert)，我试图更新datealert字段中给定用户到当前日期的所有NULL值。

Answer 1

UPDATE user_has_alerts SET dateAlerted = CURDATE() 
 WHERE userID = X AND dateAlerted IS NULL

Answer 2

UPDATE `user_has_alerts` SET `dateAlerted` = NOW() WHERE `dateAlerted` IS NULL AND userID = 1