Find the min + max value and associated column

So the database table headers are:

I'm trying to:

List item
Group by date
For each group, find the minimum buy price and the exchange associated to it
Find the maximum sellPrice and the exchange associated with it
Find the diff between max(sellPrice) - min(buyPrice)

From what I'm reading I can use rows or was there a better solution?

(Using postgresql)

Edit: If we assume we have 3 exchanges with the following data:

|Date | buyPrice | sellPrice | buyVolume | sellVolume | exchange | |1-1-2017 | 1 | 1 | 1 | 1 | exchangeA | |1-1-2017 | 2 | 1 | 2 | 1 | exchangeB | |1-1-2017 | 3 | 1 | 3 | 1 | exchangeC |

The solution output should be

Solution

Ok so I managed to get it thanks to some other questions..

SELECT t1.createdAt, t1.sellPrice, t1.exchangeId AS sellExchange, t2.buyPrice, t2.exchangeId AS buyExchange, t1.sellPrice - t2.buyPrice AS spread, 
       CASE 
         WHEN t1.sellVolume < t2.buyVolume THEN t1.sellVolume
         ELSE t2.buyVolume
       END AS minVolume
FROM 
    (SELECT a.createdAt, a.sellPrice, a.sellVolume, a.exchangeid, a.quoteId
    FROM quotes a
    INNER JOIN (
        SELECT createdAt, max(sellPrice) AS sellPrice
        FROM quotes
        GROUP BY createdAt
    ) b ON a.createdAt = b.createdAt AND a.sellPrice = b.sellPrice) 
    t1 INNER JOIN
    (SELECT a.createdAt, a.buyPrice, a.buyvolume, a.exchangeid, a.quoteId
    FROM quotes a
    INNER JOIN (
        SELECT createdAt, min(buyPrice) AS buyPrice
        FROM quotes
        GROUP BY createdAt
    ) b ON a.createdAt = b.createdAt AND a.buyPrice = b.buyPrice) 
    t2 ON t1.createdAt = t2.createdAt