MySQL创建函数失败

Question

这个

CREATE FUNCTION getTagID(tag VARCHAR(100)) RETURNS BIGINT

BEGIN
DECLARE tagID BIGINT;
            SET tagID = (SELECT id FROM tags WHERE text = tag);
IF tagID IS NULL
THEN
            (INSERT INTO tags (text) VALUES (tag));
            SET tagID = (SELECT LAST_INSERT_ID());
END IF;
RETURN tagID;
END

失败并显示

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 '' at line 4

为什么？

此函数与此处的问题相关:

mysql insert if not exists on joined tables

Answer 1

尝试更改 DELIMITER 并删除 INSERT 语句两边的括号。

DELIMITER $$
CREATE FUNCTION getTagID(tag VARCHAR(100)) 
RETURNS BIGINT
BEGIN
    DECLARE tagID BIGINT;
    SET tagID = (SELECT id FROM tags WHERE text = tag);
    IF tagID IS NULL THEN
        INSERT INTO tags (text) VALUES (tag); -- don't put inside parenthesis
        SET tagID = (SELECT LAST_INSERT_ID());
    END IF;
    RETURN tagID;
END $$
DELIMITER ;