mysql - 无法使用 IF ... THEN 语句执行查询

Question

我不能像这样执行查询:我不知道为什么:

IF(NOT EXISTS(SELECT accountId FROM test_account WHERE content = '123')) THEN
    INSERT INTO test_account (content) VALUES ('123');
END IF;
SELECT accountId FROM test_account WHERE content = '123' LIMIT 1;

收到错误:

 #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(NOT EXISTS(SELECT accountId FROM test_account WHERE content = '123')) THEN INSE' at line 1 

编辑:

我试着先写程序:

CREATE FUNCTION getTestAccount(var_c VARCHAR(20)) RETURNS INT
BEGIN
IF NOT EXISTS(SELECT accountId FROM test_account WHERE content = var_c)
THEN
    INSERT INTO test_account (content) VALUES (var_c);
END IF;
RETURN (SELECT accountId FROM test_account WHERE content = var_c LIMIT 1);
END;

我试过使用 THEN 和不使用...

甚至不能查询简单的东西:

CREATE FUNCTION getVar(var INT) RETURNS INT
BEGIN
RETURN var;
END;

Answer 1

您的函数代码看起来不错。我想知道你是否忘记在进入函数之前设置分隔符以防止MySQL被函数中的;混淆即

DELIMITER //
CREATE FUNCTION getTestAccount(var_c VARCHAR(20)) RETURNS INT
BEGIN
    IF NOT EXISTS(SELECT accountId FROM test_account WHERE content = var_c) THEN
        INSERT INTO test_account (content) VALUES (var_c);
    END IF;
    RETURN (SELECT accountId FROM test_account WHERE content = var_c LIMIT 1);
END //
DELIMITER ;