如何避免存儲過程中的遞歸調用？

我正在使用MySql存儲過程來操作我的數據庫。這裏是示例存儲過程。如何避免存儲過程中的遞歸調用？

CREATE DEFINER=`ntadmin`@`%` PROCEDURE `usp_user`(
    IN cMode  VARCHAR(20), 
    IN nUserID  MEDIUMINT UNSIGNED, 
    IN cEmail  VARCHAR(50), 
    IN cFirstName VARCHAR(20), 
    IN cLastName VARCHAR(20), 
    IN nIsMale  TINYINT(1) UNSIGNED 
) DETERMINISTIC 
BEGIN 
    IF (cMode = "insert") THEN 
     IF NOT EXISTS(SELECT 1 FROM user WHERE email = cEmail) THEN 
      INSERT INTO user(email, firstname, lastname, ismale) 
      VALUES (cEmail, cFirstName, cLastName, nIsMale); 

      SET nUserID = LAST_INSERT_ID(); 

      -- Here I would like to send all details of inserted user. 
      SET max_sp_recursion_depth = 1; 
      CALL usp_user("select", nUserID, null, null, null, null); 
     ELSE 
      SELECT -1 AS "UnSuccess", "Email already exists" AS "Error"; ;   
     END IF; 
    ELSEIF (cMode = "select") THEN 
     SELECT email, firstname, lastname, ismale 
     FROM user 
     WHERE userid = nUserID; 
    ELSEIF (cMode = "delete") THEN 
     //delete code 
     SELECT 1 AS "Success"; 
    END IF; 
END

當你仔細看我的代碼，我調用此存儲過程遞歸在使用max_sp_recursion_depth插入。有沒有更好的選擇來避免遞歸調用？

謝謝。

我應該用標籤還是GOTO聲明？避免遞歸

來源

2016-03-08 Manish Sapkal

一種選擇是改變結構如下：

mysql> DELIMITER // 

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

mysql> DROP PROCEDURE IF EXISTS `usp_user_delete`// 
Query OK, 0 rows affected (0.00 sec) 

mysql> DROP PROCEDURE IF EXISTS `usp_user_insert`// 
Query OK, 0 rows affected (0.00 sec) 

mysql> DROP PROCEDURE IF EXISTS `usp_user_select`// 
Query OK, 0 rows affected (0.00 sec) 

mysql> DROP TABLE IF EXISTS `user`// 
Query OK, 0 rows affected (0.00 sec) 

mysql> CREATE TABLE IF NOT EXISTS `user` (
    -> `nuserid` MEDIUMINT(10) UNSIGNED NOT NULL AUTO_INCREMENT, 
    -> `firstname` VARCHAR(20) DEFAULT NULL, 
    -> `lastname` VARCHAR(20) DEFAULT NULL, 
    -> `email` VARCHAR(50) DEFAULT NULL, 
    -> `ismale` TINYINT(1) UNSIGNED DEFAULT NULL, 
    -> PRIMARY KEY (`nuserid`), 
    -> UNIQUE KEY `idx_email` (`email`) 
    ->)// 
Query OK, 0 rows affected (0.01 sec) 

mysql> CREATE PROCEDURE `usp_user_insert`(
    ->  IN `cEmail` VARCHAR(50), 
    ->  IN `cFirstName` VARCHAR(20), 
    ->  IN `cLastName` VARCHAR(20), 
    ->  IN `nIsMale` TINYINT(1) UNSIGNED 
    ->) 
    -> BEGIN 
    ->  DECLARE `_existsEmail` CONDITION FOR SQLSTATE '45000'; 
    ->  IF (SELECT NOT `existsEmail`(`cEmail`)) THEN 
    ->   INSERT INTO `user` (
    ->   `email`, 
    ->   `firstname`, 
    ->   `lastname`, 
    ->   `ismale` 
    ->  ) VALUES (
    ->   `cEmail`, 
    ->   `cFirstName`, 
    ->   `cLastName`, 
    ->   `nIsMale` 
    ->  ); 
    ->   CALL `usp_user_select`(LAST_INSERT_ID()); 
    ->  ELSE 
    ->   -- SELECT -1 'UnSuccess', 'Email already exists' 'Error'; 
    ->   SIGNAL `_existsEmail` 
    ->    SET MESSAGE_TEXT = 'Email already exists', MYSQL_ERRNO = 4000; 
    ->  END IF; 
    -> END// 
Query OK, 0 rows affected (0.00 sec) 

mysql> CREATE PROCEDURE `usp_user_select`(
    ->  IN `cnuserid` MEDIUMINT UNSIGNED 
    ->) 
    -> BEGIN 
    ->  SELECT 
    ->   `email`, 
    ->   `firstname`, 
    ->   `lastname`, 
    ->   `ismale` 
    ->  FROM 
    ->   `user` 
    ->  WHERE 
    ->   `nuserid`= `cnuserid`; 
    -> END// 
Query OK, 0 rows affected (0.00 sec) 

mysql> CREATE PROCEDURE `usp_user_delete`() 
    -> BEGIN 
    ->  -- delete code 
    ->  SELECT 1 'Success'; 
    -> END// 
Query OK, 0 rows affected (0.00 sec) 

mysql> CREATE FUNCTION `existsEmail`(
    ->  `cemail` VARCHAR(50) 
    ->) RETURNS TINYINT(1) 
    -> BEGIN 
    ->  RETURN 
    ->   EXISTS(
    ->    SELECT 
    ->     NULL 
    ->    FROM 
    ->     `user` 
    ->    WHERE 
    ->     `email` = `cemail` 
    ->  ); 
    -> END// 
Query OK, 0 rows affected (0.00 sec) 

mysql> CALL `usp_user_insert`(
    ->  '[email protected]', 
    ->  'firstname_user', 
    ->  'lastname_user', 
    ->  1 
    ->)// 
+------------------+----------------+---------------+--------+ 
| email   | firstname  | lastname  | ismale | 
+------------------+----------------+---------------+--------+ 
| [email protected] | firstname_user | lastname_user |  1 | 
+------------------+----------------+---------------+--------+ 
1 row in set (0.01 sec) 

Query OK, 0 rows affected (0.01 sec) 

mysql> CALL `usp_user_insert`(
    ->  '[email protected]', 
    ->  'firstname_user', 
    ->  'lastname_user', 
    ->  1 
    ->)// 
ERROR 4000 (45000): Email already exists

來源

2016-03-09 13:52:30 wchiquito

如何避免存儲過程中的遞歸調用？

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