problem with a querry

[saddist]

Hello,
TRAININGS(ID_TRAINING, TRAINING_NAME)
HOSTED_TRAININGS(ID_HOSTED_TRAINING, ID_TRAINING, DAYS)
EMPLOYEES_ON_TRAININGS(ID_HOSTED_TRAINING)

What I want to do is a querry with sum of days and number of employees for each training

Tried something like that but it returns error "ID_HOSTED_TRAINING is not a part of aggregate function" or something like that:/

SELECT s.TRAINING_NAME AS Szkolenia, Sum(ps.DAYS), (SELECT COUNT(*) FROM EMPLOYEES_ON_TRAININGS as pns WHERE pns.ID_HOSTED_TRAINING = ps.ID_HOSTED_TRAINING)
FROM TRAININGS AS s, HOSTED_TRAININGS AS ps
WHERE (s.ID_TRAINING = ps.ID_TRAINING)
GROUP BY s.TRAINING_NAME
ORDER BY s.TRAINING_NAME;

I also tried to write COUNT function without SELECT statemant but then it counts days wrong :/
Any ideas?

[Rabbit]

Use a join instead of a Where.