How do I use a recursive procedure in a loop in MySQL - mysql

Question

I have an employees table with demographics data. This table has two fields I need: Employee ID and Manager ID. I need to build a join table that would look like this:
Employee IDManager ID
1 2
1 3
1 4
2 3
2 4
So I need the join table to show, for each employee, all the people above them. In case of employee 1 his direct manager is 2, his manager's manager is 3 and his manager's manager's manager is 4.
I have a MySQL procedure that seems to be working when called for an employee:
CREATE PROCEDURE chainReaction (IN employee_id int, IN orig_id int)
BEGIN
DECLARE manager_id int default NULL;
SET ##SESSION.max_sp_recursion_depth = 255;
SELECT ManagerID
INTO manager_id
FROM employees
WHERE EmployeeID = employee_id;
IF( manager_id is not null) THEN
INSERT INTO joinTable(EmpID, SupID) VALUES(
orig_id,manager_id
);
CALL chainReaction(manager_id, orig_id);
end if;
END;
Problem 1:
When calling chainReaction it looks like I need to provide the employee ID twice to the procedure because otherwise the original employee ID is 'lost' and the resulting inserts for employee 1 look like this:
Employee IDManager ID
1 2
2 3
4 4
So the Employee ID doesn't stay fixed to 1 as I needed it. Again, this procedure works when called as it is now: chainReaction(1,1);
But here's problem 2:
I have some code to loop through all rows in the employee table and call chainReaction on them:
CREATE PROCEDURE RowPerRow ()
BEGIN
DECLARE n int default 0;
DECLARE i int default 0;
DECLARE employee_id int default null;
SELECT COUNT(*) FROM employees INTO n;
SET i=0;
WHILE i<n DO
SELECT EmployeeID FROM employees WHERE LIMIT i,1 INTO employee_id;
CALL chainReaction(employee_id,employee_id);
END WHILE;
END;
The problem is that if I call this RowPerRow() procedure the employee column in the join table is stuck to the first employee ID no matter what row is being processed.

Answer 1

Looks like my procedures work just fine, what I was missing in the RowPerRow procedure is incrementing the counter (SET i = i + 1;). Here's the code fixed.
CREATE PROCEDURE RowPerRow ()
BEGIN
DECLARE n int default 0;
DECLARE i int default 0;
DECLARE employee_id int default null;
SELECT COUNT(*) FROM employees INTO n;
SET i=0;
WHILE i<n DO
SELECT EmployeeID FROM employees WHERE LIMIT i,1 INTO employee_id;
CALL chainReaction(employee_id,employee_id);
SET i = i + 1;
END WHILE;
END;