想用IF控制执行语句SQL报错这个是什么错误

以下是SQL

IF (SELECT 1 = 1 FROM item WHERE tasknumber=1230) THEN
BEGIN
    SELECT * FROM item;
END;
ELSE
BEGIN
    SELECT * FROM item;
END;
END IF;

报错信息

IF (SELECT 1 = 1 FROM item WHERE tasknumber=1230) THEN
BEGIN
    SELECT * FROM item
1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IF (SELECT 1 = 1 FROM item WHERE tasknumber=1230) THEN
BEGIN
    SELECT * FROM' at line 1
时间: 0s

这东西，只能在存储过程，自定义函数里使用。

sql里要使用case when then语法，不要使用if