MySQL, Problem using CONCAT in stored procedure

Question

I am having a problem using CONCAT() in a MySQL procedure.

I am using MySQL version: 8.0.22

From the command line, CONCAT works for the following two scenarios. So, it appears to me that I should be able to use one of these formats in a procedure.

root@localhost [mdy_exp_constraints]> SET @primary_color_name = 'yellow';
Query OK, 0 rows affected (0.00 sec)

root@localhost [mdy_exp_constraints]> SELECT CONCAT('Data too short for ', @primary_color_name, ' column.');
+----------------------------------------------------------------+
| CONCAT('Data too short for ', @primary_color_name, ' column.') |
+----------------------------------------------------------------+
| Data too short for yellow column.                              |
+----------------------------------------------------------------+
1 row in set (0.00 sec)


root@localhost [mdy_exp_constraints]> SET @woof =  CONCAT('Data too short for ', @primary_color_name, ' column.');
Query OK, 0 rows affected (0.00 sec)

root@localhost [mdy_exp_constraints]> SELECT @woof;
+-----------------------------------+
| @woof                             |
+-----------------------------------+
| Data too short for yellow column. |
+-----------------------------------+
1 row in set (0.00 sec)

This is the data that I use to test my procedure

• This is good data. So, no errors to report.

CALL mdy_exp_constraints.checkColorsForTooFewChars('red', 'ff');
Query OK, 0 rows affected (0.00 sec)

• This is bad data because the data is too long for IN primary_color_value CHAR(2) . This error is handled by the MySQl server.

CALL mdy_exp_constraints.checkColorsForTooFewChars('green', 'fff');
ERROR 1406 (22001): Data too long for column 'primary_color_value' at row 1

• This is bad data because the data is too short for CHAR(2). What I am trying to do is to report this error. BUT, it does not seem to like how I am using CONCAT() in a procedure.

CALL mdy_exp_constraints.checkColorsForTooFewChars('blue', 'a');
ERROR 1644 (45000): Data too short for column.

Below, I define my procedure.

CREATE SCHEMA mdy_exp_constraints
DEFAULT CHARACTER SET utf8mb4
COLLATE utf8mb4_0900_ai_ci;

USE mdy_exp_constraints;


DROP PROCEDURE IF EXISTS mdy_exp_constraints.checkColorsForTooFewChars;
SHOW COUNT(*) WARNINGS;
SHOW WARNINGS;


# -- SHOW all PROCEDUREs for the specified database.
SHOW
    PROCEDURE STATUS
WHERE
    db = 'mdy_exp_constraints'\G


DELIMITER $

CREATE PROCEDURE checkColorsForTooFewChars(
    IN primary_color_name VARCHAR(32),
    IN primary_color_value CHAR(2)
)
BEGIN
    DECLARE required_str_length TINYINT;
    SET required_str_length = 2;

    IF CHAR_LENGTH(primary_color_value) < required_str_length THEN
        SIGNAL SQLSTATE '45000'
            SET MESSAGE_TEXT = CONCAT('Data too short for ', primary_color_name, ' column.');
            -- SET MESSAGE_TEXT = 'Data too short for column.';
    END IF;
END $

DELIMITER ;

And this is the error that I am receiving.

ERROR 1064 (42000): 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 '('Data too short for ', primary_color_name, ' column.');
            
    END IF' at line 11

If I comment out the line that contains the CONCAT() and un-comment the line not containing the CONCAT(), this procedure works when running it against the test data...except, that it will not report the primary_color_name , which is what I would like for it to do.

Thanks,

Mike

Answer 1

The error occurs because SET MESSAGE_TEXT does not accept expressions.

DELIMITER $

CREATE PROCEDURE checkColorsForTooFewChars(
    IN primary_color_name VARCHAR(32),
    IN primary_color_value CHAR(2)
)
BEGIN
    DECLARE required_str_length TINYINT;
    SET required_str_length = 2;

    IF CHAR_LENGTH(primary_color_value) < required_str_length THEN
        SET @errorMsg = CONCAT('Data too short for ', primary_color_name, ' column.');
        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = @errorMsg;
    END IF;
END $

DELIMITER ;

fiddle