Postgres - How to Join Tables without duplicates - django

Question

I'm working on a project that locally used SQLite, now when moving to PostGres (On Heroku) my query reported an error "r.social must appear in the GROUP BY clause or be used in an aggregate function"
The original query is:
SELECT DISTINCT c.name, r.social, c.description, p.price
FROM cryptomodels_coin c
LEFT JOIN cryptomodels_coinprice p
ON p.coin_id = c.name
LEFT JOIN cryptomodels_CoinRating r
ON r.coin_id = c.name
GROUP BY c.name
Which works fine locally, with one unique row returned for each coin
When I added this to the PostGres environment, it threw the aggregate function error mentioned above - I managed to resolve this by adding all columns to the "Group by" clause, as seen below:
SELECT DISTINCT c.name, r.social, c.description, p.price
FROM cryptomodels_coin c
LEFT JOIN cryptomodels_coinprice p
ON p.coin_id = c.name
LEFT JOIN cryptomodels_CoinRating r
ON r.coin_id = c.name
GROUP BY c.name, r.social, c.description, p.price
The issue is that I now have duplicate rows for each coin
I've done a fair bit of reading and tried numerous solutions, some of which throw errors and others still result in duplicate rows, really not sure how to proceed, thank you for any assistance
EDIT for additional information:
Each coin has numerous prices and numerous ratings, with the cryptomodels_coin table being referenced by the other tables by using it's name as "coin_id" the so three coins for example:
Coin table:
| Name |
--------
| 0X |
| XSV |
| BTC |
Price table:
| Coin_id | Price |
-------------------
| 0X | 43.2 |
| XSV | 20.0 |
| BTC | 99999|
Rating table:
| Coin_id | Social|
-------------------
| 0X | 20,000|
| XSV | 12,000|
| BTC | 5,0000|
EDIT 2:
CREATE TABLE "cryptomodels_coin" (
"name" varchar(200) NOT NULL PRIMARY KEY,
"description" text NOT NULL);
CREATE TABLE "cryptomodels_coinprice" (
"id" integer NOT NULL PRIMARY KEY AUTOINCREMENT,
"price" real NULL,
"coin_id" varchar(200) NOT NULL REFERENCES "cryptomodels_coin" ("name") );
CREATE TABLE "cryptomodels_coinrating" (
"id" integer NOT NULL PRIMARY KEY AUTOINCREMENT,
"social" text NULL, "coin_id" varchar(200) NOT NULL REFERENCES "cryptomodels_coin" ("name"));
Added SQLFiddle:
http://sqlfiddle.com/#!15/9fcff/1
Thanks!

Answer 1

I guess something like this would eliminate duplicates as you wish:
SELECT c.name AS name,
r.social AS social,
c.description AS description,
SUM(p.price) AS price
FROM cryptomodels_coin c
LEFT JOIN cryptomodels_coinprice p ON p.coin_id = c.name
LEFT JOIN cryptomodels_CoinRating r ON r.coin_id = c.name
GROUP BY c.name,r.social,c.description