Count and group with a ref

[VictorB]

Hi every one, 

I'm a French novice on Appsheet, I'm struggling with a formula. 

I try to count the number of elements that match a criteria (yes or no) and to organise them by group. 

I have tow Tables : Data_light_spot and Groups with a reference between them.

Data_light_spot : 

Group, Number, Working

AA, 01, Yes

AA, 02, Yes

AA, 02, No

AB, 01, Yes

AB, 02 No

....

Groups :

Group, How many (total), How many working

AA, 3, 2

AB, 2, 1

...

I've first use the virtual row Related Data_light_spot with count()  to find out the value of the column How many (total).

But I can't find a way to count the numbers of "Yes" from the table Data_light_spot and to "group" them into the table Groups. 

hanks for the help