MySQL db Audit Trail Trigger

I need to track changes (audit trail) on specific tables in MySql Db. I am trying to implement the suggested solution here .

I have an AuditLog table with the following columns: AuditLogID, TableName, RowPK, FieldName, OldValue, NewValue, TimeStamp.

The mysql stored procedure is as follows (this runs fine and creates a procedure):

Calling a procedure such as: CALL addLogTrigger ('ProductTypes', 'ProductTypeID'); executes but does not create any triggers (see image). SHOW TRIGGERS returns an empty set.

Please let me know what the problem might be, or an alternative way to implement this.

    DROP PROCEDURE IF EXISTS addLogTrigger;
DELIMITER $
CREATE PROCEDURE addLogTrigger(IN tableName VARCHAR(255), IN pkField VARCHAR(255))
BEGIN

    SELECT CONCAT(
    'DELIMITER $\n', 'CREATE TRIGGER ', tableName, '_AU AFTER UPDATE ON ', tableName, ' FOR EACH ROW BEGIN ',
        GROUP_CONCAT(
            CONCAT(
          'IF NOT( OLD.', column_name, ' <=> NEW.', column_name, ') THEN INSERT INTO AuditLog (',
                    'TableName, ',
                    'RowPK, ',
                    'FieldName, ',
                    'OldValue, ',
                    'NewValue'
                    ') VALUES ( ''',
                    table_name, ''', NEW.',
                    pkField, ', ''',
                    column_name, ''', OLD.',
                    column_name, ', NEW.',
                    column_name,
                '); END IF;'
            )
            SEPARATOR ' '
            ), ' END;$'
        ) 
        FROM 
            information_schema.columns 
        WHERE 
            table_schema = database()
            AND table_name = tableName;

END$
DELIMITER ;

      

        
        
        
      

    

alt text http://pssnet.com/~devone/pssops3/testing/callprocedure.png