Query to calculate the proportion [duplicate]

Question

I am new to SQL (using SQLiteStudio) and I wrote such a query to calculate Proportion for each group ( number of rooms) from the total sale of apartments. But it doesn't calculate correctly. Give a result of 100 for each group. I don't know what I'm doing wrong can you guys help in any way? Thanks!

    1. SELECT 
    2.l.num_rooms as "Number",
    3.count(l.id_locale) as "Number sales",
    4.round(count (l.id_locale)/
    5.(SELECT count (l.type_locale)FROM locale 
    6.WHERE l.type_locale = 'Appartement' )*100,2) as "Proportion"
    7.FROM locale l
    8.WHERE l.type_locale = 'Appartement' 
    9.GROUP BY l.num_rooms
    10.ORDER BY l.num_rooms;

type_locale	surface	num_rooms	fk_lieu	id_locale
Appartement	52	1	45	1
Appartement	45	2	67	21
Appartement	12	3	34	78
Appartement	67	2	89	12
Appartement	31	1	15	56

Answer 1

I see two problems in your code: 1) You are using and integer division (2/5 = 0); 2) the subquery is a correlated one while it should be unrelated to a main query. So use another alias in the subquery and convert at least one of the arguments in the expression to real.

SELECT  l.num_rooms as "Number",
    count(l.id_locale) as "Number sales",
    round(count(l.id_locale)*1.0 /
       (SELECT count(l2.id_locale) FROM locale l2
        WHERE l2.type_locale = 'Appartement' )*100,2) as "Proportion"
FROM locale l
WHERE l.type_locale = 'Appartement' 
GROUP BY l.num_rooms
ORDER BY l.num_rooms;