MySQL handle duplicate key error insert into table with multiple unique indexes; not multi-column unique index

Question

How do I find which unique index has failed from within a stored procedure?

I have created a table with a single column primary key and three single column unique indexes:

CREATE TABLE tableName (
  id INT UNSIGNED NOT NULL AUTO_INCREMENT,
  col1 VARCHAR(50) NOT NULL,
  col2 VARCHAR(50) NOT NULL,
  col3 VARCHAR(50) NOT NULL,
  PRIMARY KEY (id),
  UNIQUE INDEX id_UNIQUE (id ASC),
  UNIQUE INDEX col1_UNIQUE (col1 ASC),
  UNIQUE INDEX col2_UNIQUE (col2 ASC),
  UNIQUE INDEX col3_UNIQUE (col3 ASC)
) ENGINE = InnoDB;

I have create a stored procedure that handles Error '1062': 'Duplicate entry %s for key %d':

DELIMITER $$
CREATE PROCEDURE insertRecord (
        col1Value   VARCHAR(50), 
        col2Value   VARCHAR(50), 
        col3Value   VARCHAR(50), 
    OUT idValue     INT,
    OUT errColName  VARCHAR(50)
) BEGIN
    DECLARE EXIT HANDLER FOR 1062 BEGIN
        SET errColName = 'Insert Column Name Here';
    END;

    INSERT tableName SET
        col1 = col1Value, 
        col2 = col2Value, 
        col3 = col3Value;

    SET idValue = LAST_INSERT_ID();
END;
$$
DELIMITER ;

I have called the stored procedure 5 times with different data to return various results:

1st INSERT attempt is successful

-- Initialize parameters
SET @col1Val = 'MySQL', 
    @col2Val = 'Is', 
    @col3Val = 'Cool', 
    @Id = NULL, 
    @ErrColName = NULL;
-- 1st Insert Attempt
CALL insertRecord(@col1Val, @col2Val, @col3Val, @Id, @ErrColName);
-- Expected result: @Id = 1, @ErrColName = NULL
SELECT @Id '@Id', @ErrColName '@ErrColName';

2nd INSERT Attempt fails because col1 is not unique

-- Re-initialize parameters
SET @col1Val = 'MySQL', -- Intended to generate an error
    @col2Val = 'Is', 
    @col3Val = 'Cool', 
    @Id = NULL, 
    @ErrColName = NULL;
-- 2nd Insert Attempt
CALL insertRecord(@col1Val, @col2Val, @col3Val, @Id, @ErrColName);
-- Expected result: @Id = NULL, @ErrColName = 'col1'
SELECT @Id '@Id', @ErrColName '@ErrColName';

3rd INSERT Attempt fails because col2 is not unique

-- Re-initialize parameters
SET @col1Val = 'SQL', 
    @col2Val = 'Is', -- Intended to generate an error
    @col3Val = 'Cool', 
    @Id = NULL, 
    @ErrColName = NULL;
-- 3rd Insert Attempt
CALL insertRecord(@col1Val, @col2Val, @col3Val, @Id, @ErrColName);
-- Expected result: @Id = NULL, @ErrColName = 'col2'
SELECT @Id '@Id', @ErrColName '@ErrColName';

4th INSERT Attempt fails because col3 is not unique

-- Re-initialize parameters
SET @col1Val = 'SQL', 
    @col2Val = 'For', 
    @col3Val = 'Cool', -- Intended to generate an error
    @Id = NULL, 
    @ErrColName = NULL;
-- 4th Insert Attempt
CALL insertRecord(@col1Val, @col2Val, @col3Val, @Id, @ErrColName);
-- Expected result: @Id = NULL, @ErrColName = 'col3'
SELECT @Id '@Id', @ErrColName '@ErrColName';

5th INSERT Attempt is successful

-- Re-initialize parameters
SET @col1Val = 'SQL', 
    @col2Val = 'For', 
    @col3Val = 'Life', 
    @Id = NULL, 
    @ErrColName = NULL;
-- 5th Insert Attempt
CALL insertRecord(@col1Val, @col2Val, @col3Val, @Id, @ErrColName);
-- Expected result: @Id = 5, @ErrColName = NULL
SELECT @Id '@Id', @ErrColName '@ErrColName';

What do I need to do in the stored procedure to find which unique index has failed from within a stored procedure?

Thanks in advance.

Answer 1

I found the answer under Which unique key is hit with my insert?. It is not ideal however does solve the problem.

The following is the applied solution:

    ...
    DECLARE EXIT HANDLER FOR 1062 BEGIN
        -- Check if col1Value is already in use
        IF EXISTS (
            SELECT 1
            FROM tableName
            WHERE col1 = col1value
            LIMIT 1
        ) THEN
            SET errColName = 'Col1';

        -- Check if col2Value is already in use
        ELSEIF EXISTS (
            SELECT 1
            FROM tableName
            WHERE col2 = col2value
            LIMIT 1
        ) THEN
            SET errColName = 'Col2';

        -- Check if col3Value is already in use
        ELSEIF EXISTS (
            SELECT 1
            FROM tableName
            WHERE col3 = col3value
            LIMIT 1
        ) THEN
            SET errColName = 'Col3';

        END IF;
    END;
    ...