SQL - update only if subquery is not null

Question

I want to update last_test_date only when there are entries in car_log without status 'test' and I really think this code is horrible, is there any way how to write it better?

UPDATE car SET last_test_date = 
(SELECT date FROM car_log WHERE car_log.car_id = car.id AND
car_log.status != 'test' ORDER BY date DESC LIMIT 0,1)
WHERE (SELECT COUNT(*) FROM car_log WHERE car_log_id = client.id AND
car_log.status != 'test') > 0;

Answer 1

Use @@ROWCOUNT to get the last query rows count, this way you will not repeat the select

...
WHERE @@ROWCOUNT > 0;

Answer 2

An update join syntax will make your statement much clearer:

UPDATE car 
JOIN   (SELECT car_id, MAX(date) AS max_date
        FROM   car_log
        WHERE  car_log.status != 'test') ON car_log.car_id = car.id AND
SET    last_test_date = max_date