我想要的代码是，如果任何新列的值为空 将其更改为ROW BEFORE WITH TRIGGER EVENT的值
CREATE TRIGGER updateField BEFORE INSERT ON message
FOR EACH ROW
IF (NEW.COLUMN IS NULL) then
set NEW.COLUMN = SELECT THE_COLUMN FROM Table ORDER BY ID DESC LIMIT 1;
END IF
你还必须有BEGIN分和END分.
如果您有超过一个代码行
DELIMITER $$
CREATE TRIGGER updateField BEFORE INSERT ON message
FOR EACH ROW
BEGIN
IF (NEW.COLUMN IS NULL) then
set NEW.COLUMN = (SELECT THE_COLUMN FROM Table1 ORDER BY ID DESC LIMIT 1);
END IF;
END$$
DELIMITER ;