Use parentheses
SELECT * FROM cars
WHERE (carBrand LIKE '%alfa%' OR carModel LIKE '%alfa%')
AND carType = 'truck'
AND
binds stronger than OR
. It's called Operator Precedence. Without parentheses your query compiles to
SELECT * FROM cars
WHERE carBrand LIKE '%alfa%'
OR (carModel LIKE '%alfa%' AND carType = 'truck')