Joining Two tables Based on Third Table (SQLite)

Question

I'm trying to use three different tables to get a list of all McDonald's in the US, sorted by number of Burger Kings within 100 miles. For some reason, I'm having a really hard time wrapping my head around this problem, and I'm wondering if anyone can offer any suggestions on how they might approach a problem like this?

I have a table of all McDonald's with their zip codes, a table of all zip codes with number of burger kings, and a table of all zip codes within 100 miles of each other. For example:

Mcdonalds table:

NAME	zip
McDonalds Park Terrace	11121
McDonalds HWY 103	11412
McDonalds Crestwood	11121
McDonalds Pendleton	26566
McDonalds Smithville	67742
McDonalds HWY 66	43351

BKzips table:

zip	numberBKs
11121	2
11412	0
26566	6
43351	0
67742	3
...	...

zipproximity table:

zip1	zip2	distancebetween
11121	11412	23.443
11121	26566	48.211
...	...	...
11412	11121	23.443

My desired end result is a table with a row for each mcdonalds, listing all zips within 100 mi of that mcdonalds and their total number of BKs. For example:

McDonalds	zip	zipsWithBKs	totalBKs
McDonalds Park Terrace	11121	26566, 11412	6

I've been able to use inner joins to get a table with one row per zip with BKs:

SELECT McDonalds.NAME, BKzips.zip, BKzips.numberBKs
FROM zipproximity
    INNER JOIN McDonalds
        ON zipproximity.zip1 = McDonalds.zip
    INNER JOIN BKzips 
        ON zipproximity.zip2 = BKzips.zip

But I can't figure out how to get my desired result. Between not being experienced with SQL and working this problem for hours I'm pretty stuck. I appreciate any help!

Answer 1

Nearly there, just a GROUP BY and some aggregation functions:

SELECT McDonalds.NAME, McDonalds.zip, GROUP_CONCAT(BKzips.zip, ', ') AS zipsWithBKs, SUM(BKzips.numberBKs) AS totalBKs
FROM zipproximity
    INNER JOIN McDonalds
        ON zipproximity.zip1 = McDonalds.zip
    INNER JOIN BKzips 
        ON zipproximity.zip2 = BKzips.zip
-- WHERE BKzips.numberBKs > 0   -- you probably want this also
GROUP BY McDonalds.NAME, McDonalds.zip;