How to avoid recursive call in stored procedure? - mysql

Question

I am using MySql stored procedure to do operation with my database.
Here is sample store procedure.
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
As you look carefully my code, I am calling this stored procedure recursively in insert using max_sp_recursion_depth. Is there any better option to avoid recursive call?
Thanks.
Should I use Label or GOTO statements?

Answer 1

One option to avoid recursion is changing the structure as follows:
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`(
-> 'user#example.com',
-> 'firstname_user',
-> 'lastname_user',
-> 1
-> )//
+------------------+----------------+---------------+--------+
| email | firstname | lastname | ismale |
+------------------+----------------+---------------+--------+
| user#example.com | 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`(
-> 'user#example.com',
-> 'firstname_user',
-> 'lastname_user',
-> 1
-> )//
ERROR 4000 (45000): Email already exists