How to leave negative number according to condition - Mysql Trigger

  

I need the valor field to have the minus sign if is equal to tipo every time I enter and update.

Pro development, I created the 0 table with the following structure :

+-------+---------+------+-----+---------+----------------+
| Field | Type    | Null | Key | Default | Extra          |
+-------+---------+------+-----+---------+----------------+
| id    | int(10) | NO   | PRI | NULL    | auto_increment |
| tipo  | int(2)  | YES  |     | NULL    |                |
| valor | float   | YES  |     | NULL    |                |
+-------+---------+------+-----+---------+----------------+

Creating the trigger ) :

DELIMITER $$

CREATE TRIGGER gatilho_update
    BEFORE UPDATE ON 'lc_movimento'
    FOR EACH ROW
        BEGIN
            SET @tipo = NEW.tipo;
            SET @valor = NEW.valor;
                IF( @tipo = 0 ) THEN
                    SET NEW.valor = ( @valor * (-1) );
                ELSE
                    SET NEW.valor = @valor;
                END IF;
        END$$

CREATE TRIGGER gatilho_insert
    BEFORE INSERT ON 'lc_movimento'
    FOR EACH ROW
        BEGIN
            SET @tipo = NEW.tipo;
            SET @valor = NEW.valor;
                IF( @tipo = 0 ) THEN
                    SET NEW.valor = ( @valor * (-1) );
                ELSE
                    SET NEW.valor = @valor;
                END IF;
        END$$

DELIMITER ;

Inserting Data (Testing) :

INSERT INTO 'lc_movimento' ('tipo', 'valor') VALUES (1, 1234), (0, 17), (0, 83547), (1, 8637), (1, 1234), (0, 83142);

Checking data :

mysql> SELECT * FROM 'lc_movimento';
+----+------+--------+
| id | tipo | valor  |
+----+------+--------+
|  1 |    1 |   1234 |
|  2 |    0 |    -17 |
|  3 |    0 | -83547 |
|  4 |    1 |   8637 |
|  5 |    1 |   1234 |
|  6 |    0 | -83142 |
+----+------+--------+
6 rows in set (0.00 sec)

SELECT id, tipo, 
 CASE 
   WHEN tipo = 0 THEN valor*-1
   WHEN tipo <> 0 THEN valor
 END AS valor
FROM lc_movimento

case does the test, and multiplication by -1 converts to negative.