Store Procedure Concat a select while in a loop - mysql

Question

I'm building a serie of Procedures where I'll have to insert generic names in almost all of them, and multiples columns.
So I thought in create a Procedure to Generate a "text" for me. The code for the text is this:
SELECT CONCAT( CHAR( FLOOR(65 + (RAND() * 25))));
This generates one random char for me. So this is the procedure that I made:
DELIMITER ;;
CREATE DEFINER=`my_definer`#`localhost` PROCEDURE GenericName(IN NumRows INT,OUT retorno VARCHAR)
BEGIN
DECLARE i INT;
SET i = 1;
SET retorno = "";
WHILE i <= NumRows DO
SET retorno = SELECT CONCAT( CHAR( FLOOR(65 + (RAND() * 25))));
SET i = i + 1;
END WHILE;
END;;
DELIMITER ;
The following error is what is appearing when I try to create the procedure:
You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use
near ') BEGIN DECLARE i INT; SET i = 1; SET retorno = "";
Based on the error, I think is something stupid, but I don't have much of expertise in creating Store Procedures and I may be overthinking something.
PS (this is the future usage that I'm planing to do when I finish the procedure above): The idea is to call this procedure in other procedures by something like:
INSERT INTO tbl_a (name, position) VALUES (CALL GenericName(7), CALL GenericName(5));
External links:
I saw that is possible to call a procedure from another procedure here "Calling a Stored Procedure in a Stored Procedure in MySQL"

Answer 1

PROBLEM #1
You should not be using a Stored Procedure. You should be using a Stored Function
PROBLEM #2
In the loop, you forgot to include retorno in the CONCAT
PROBLEM #3
Also, I would change
CHAR(FLOOR(65 + (RAND() * 25)))
to
CHAR(FLOOR(65.5 + (RAND() * 25)))
to give the letter Z a fair chance to appear
PROBLEM #4
Replace
SET retorno = SELECT CONCAT(...
with
SET retorno = CONCAT(...
PROPOSED STORED FUNCTION
DELIMITER ;;
CREATE DEFINER=`my_definer`#`localhost` FUNCTION GenericName
(NumRows INT)
RETURNS VARCHAR(20)
DETERMINISTIC
BEGIN
DECLARE i INT;
DECLARE retorno VARCHAR(20);
SET i = 1;
SET retorno = "";
WHILE i <= NumRows DO
SET retorno = CONCAT(retorno,CHAR(FLOOR(65.5 + (RAND() * 25))));
SET i = i + 1;
END WHILE;
RETURN retorno;
END;;
DELIMITER ;
Then, you can call the INSERT like this
INSERT INTO tbl_a (name, position) VALUES (GenericName(7),GenericName(5));
GIVE IT A TRY !!!