mysql - 我的MySQL函数未插入值

这是我的代码：

IF EXISTS(SELECT * FROM User WHERE Username = @Username) THEN
    RETURN -1;
ELSEIF EXISTS(SELECT * FROM User WHERE Email = @Email)
THEN
    RETURN -2;
ELSE
    INSERT INTO User(Username, Password, Email)
    VALUES ('Nicki',@Password,@Email);
    RETURN LAST_INSERT_ID();
END IF

还有一张图片



但是该函数不会插入值-您能解释为什么吗？

最佳答案

@Username是9.4 User-Defined Variables，Username是表列。

另外，请检查：C.1 Restrictions on Stored Programs::Name Conflicts within Stored Routines。

尝试：

mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.18    |
+-----------+
1 row in set (0.00 sec)

mysql> DROP FUNCTION IF EXISTS `InsertUser`;
Query OK, 0 rows affected (0.00 sec)

mysql> DROP TABLE IF EXISTS `User`;
Query OK, 0 rows affected (0.01 sec)

mysql> CREATE TABLE IF NOT EXISTS `User`(
    ->   `Id` BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    ->   `Username` VARCHAR(255) NOT NULL,
    ->   `Password` VARCHAR(255) NOT NULL,
    ->   `Email` VARCHAR(255) NOT NULL
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER //

mysql> CREATE FUNCTION `InsertUser`(`_Username` VARCHAR(255),
    ->                              `_Email` VARCHAR(255),
    ->                              `_Password` VARCHAR(255)
    -> )
    -> RETURNS INT
    -> LANGUAGE SQL
    -> DETERMINISTIC
    -> MODIFIES SQL DATA
    -> BEGIN
    ->   IF EXISTS(SELECT * FROM `User` WHERE `Username` = `_Username`) THEN
    ->     RETURN -1;
    ->   ELSEIF EXISTS(SELECT * FROM `User` WHERE `Email` = `_Email`) THEN
    ->     RETURN -2;
    ->   ELSE
    ->     INSERT INTO `User` (`Username`, `Password`, `Email`)
    ->     VALUES ('Nicki', `_Password`, `_Email`);
    ->     RETURN LAST_INSERT_ID();
    ->   END IF;
    -> END//
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER ;

mysql> SELECT
    ->   `Id`,
    ->   `Username`,
    ->   `Password`,
    ->   `Email`
    -> FROM
    ->   `User`;
Empty set (0.00 sec)

mysql> SELECT `InsertUser`(NULL, 'pass', '[email protected]');
+------------------------------------------------+
| `InsertUser`(NULL, 'pass', '[email protected]') |
+------------------------------------------------+
|                                              1 |
+------------------------------------------------+
1 row in set (0.01 sec)

mysql> SELECT
    ->   `Id`,
    ->   `Username`,
    ->   `Password`,
    ->   `Email`
    -> FROM
    ->   `User`;
+----+----------+------------------+-------+
| Id | Username | Password         | Email |
+----+----------+------------------+-------+
|  1 | Nicki    | [email protected] | pass  |
+----+----------+------------------+-------+
1 row in set (0.00 sec)

mysql> SELECT `InsertUser`(NULL, 'pass', '[email protected]');
+------------------------------------------------+
| `InsertUser`(NULL, 'pass', '[email protected]') |
+------------------------------------------------+
|                                             -2 |
+------------------------------------------------+
1 row in set (0.00 sec)

示例db-fiddle。