SQL - Count rows based on matching columns and value range - sql

Question

Please see below query using T-SQL with SSMS. There are three tables: B, G and L.
B has a column Bname
G has 2 columns Gname, Gross
L has 2 columns Bname, Gname
Gross column is an INT ranging values between 80 and 100.
Table L's columns: Bname and Gname will feature names from the B and G tables on the same row. Where both names feature on the same row, I would like to COUNT this as one item; only if the Gross on Table G ranges between 80 and 100 to the corresponding Gname row.
My current query reads:
SELECT l.bname, (SELECT COUNT(*) FROM g WHERE g.gross BETWEEN 80 AND 90) AS Good
FROM l
INNER JOIN b
ON b.bname=l.bname
INNER JOIN g
ON g.gname=l.gname
GROUP BY l.bname;
The result is nearly there, but it counts all Table G:Gname rows betweeen 80 and 100. Emitting the instances on Table L where the Bname and Gname are on the same row.
Thanks in advance for looking.

Answer 1

I suspect that you want:
SELECT l.bname,
(SELECT COUNT(*)
FROM b INNER JOIN
g
ON g.gname = l.gname
WHERE b.bname = l.bname AND g.gross BETWEEN 80 AND 90
) AS Good
FROM l ;
The outer aggregation is not needed of l.bname is unique.
This would more commonly be calculating using conditional aggregation:
SELECT l.bname,
SUM(CASE WHEN g.gross BETWEEN 80 AND 90 THEN 1 ELSE 0 END) AS Good
FROM l INNER JOIN
b
ON b.bname = l.bname INNER JOIN
g
ON g.gname = l.gname
GROUP BY l.bname;
No subquery is needed.