MySQL - Using SELECT INTO statement inside cursor in stored procedure - mysql

Question

I am writing stored procedure in MySQL database using cursor to iterate on records. I am able to fetch records inside variables specified in FETCH statement, but when I use SELECT inside cursor, I am not able to store result in variables. I know its possible but can't find out why its not working in below MySQL code.
CREATE DEFINER=`root`#`localhost` PROCEDURE `add_monthly_leave_entitlement`
(IN `emp` INT(10), OUT `experience` INT(10), OUT `entitlement` DECIMAL(10,4)) DETERMINISTIC
BEGIN
DECLARE emp_no INT(10);
DECLARE current_month_exp INT(10);
DECLARE previous_month_end_exp INT(10);
DECLARE emp_status INT(10);
DECLARE done INT DEFAULT FALSE;
DECLARE monthly_entitlement decimal(8,4) DEFAULT 0;
DECLARE emp_cursor CURSOR FOR
SELECT e.`emp_number` AS emp_no,
TIMESTAMPDIFF( YEAR, e.`joined_date` , NOW( ) ) AS month_start_exp,
TIMESTAMPDIFF( YEAR, e.`joined_date`, LAST_DAY(NOW()- INTERVAL 1 MONTH) ) AS last_month_end_exp, e.`emp_status` AS emp_status
FROM `hs_hr_employee` AS e
WHERE e.`termination_id` is null AND e.`emp_number`=emp;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN emp_cursor;
read_loop : LOOP
FETCH emp_cursor INTO emp_no, current_month_exp, previous_month_end_exp, emp_status;
IF done THEN
LEAVE read_loop;
END IF;
/*Monthly entitlement as per experience*/
SELECT `monthly_entitlement` INTO monthly_entitlement
FROM `ohrm_leave_entitlement_conf`
WHERE `year_completion` = IF(previous_month_end_exp >4 , 5, previous_month_end_exp)
AND `leave_type_id` = 4;
SET experience = previous_month_end_exp;
SET entitlement = monthly_entitlement;
END LOOP;
CLOSE emp_cursor;
END
Not able to get value inside monthly_entitlement or entitlement, the value is always 0.0000.
I tried to run monthly entitlement query in separate procedure, it returns correct value. I have match data types of table column and variables.
Can somebody help me to understand what is wrong here ?

Answer 1

Avoid naming local variables as columns name, see Chapter 2 Restrictions on Stored Programs :: Name Conflicts within Stored Routines. Try changing the following:
...
-- DECLARE monthly_entitlement decimal(8,4) DEFAULT 0;
DECLARE _monthly_entitlement decimal(8,4) DEFAULT 0;
...
/*Monthly entitlement as per experience*/
-- SELECT `monthly_entitlement` INTO monthly_entitlement
SELECT `monthly_entitlement` INTO _monthly_entitlement
...
-- SET entitlement = monthly_entitlement;
SET entitlement = _monthly_entitlement;
...

Answer 2

As suggested by others the Name of the local variable and the column name should be different, So here the changes
CREATE DEFINER=`root`#`localhost` PROCEDURE `add_monthly_leave_entitlement`
(IN `emp` INT(10), OUT `experience` INT(10), OUT `entitlement` DECIMAL(10,4)) DETERMINISTIC
BEGIN
DECLARE v_emp_no INT(10);
DECLARE v_current_month_exp INT(10);
DECLARE v_previous_month_end_exp INT(10);
DECLARE v_emp_status INT(10);
DECLARE done INT DEFAULT FALSE;
DECLARE v_monthly_entitlement decimal(8,4) DEFAULT 0;
DECLARE emp_cursor CURSOR FOR
SELECT e.`emp_number` AS emp_no,
TIMESTAMPDIFF( YEAR, e.`joined_date` , NOW( ) ) AS month_start_exp,
TIMESTAMPDIFF( YEAR, e.`joined_date`, LAST_DAY(NOW()- INTERVAL 1 MONTH) ) AS last_month_end_exp, e.`emp_status` AS emp_status
FROM `hs_hr_employee` AS e
WHERE e.`termination_id` is null AND e.`emp_number`=emp;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN emp_cursor;
read_loop : LOOP
FETCH emp_cursor INTO v_emp_no, v_current_month_exp, v_previous_month_end_exp, v_emp_status;
IF done THEN
LEAVE read_loop;
END IF;
/*Monthly entitlement as per experience*/
SELECT `monthly_entitlement` INTO v_monthly_entitlement
FROM `ohrm_leave_entitlement_conf`
WHERE `year_completion` = IF(v_previous_month_end_exp >4 , 5, v_previous_month_end_exp)
AND `leave_type_id` = 4;
SET experience = v_previous_month_end_exp;
SET entitlement = v_monthly_entitlement;
END LOOP;
CLOSE emp_cursor;
END