有什么方法可以將DISTINCT的結果分組並正確地將COUNT行分組？

Question

我有這個查詢：

SELECT DISTINCT w.buyer_id, u.username, a.cb_id
FROM winners AS w
INNER JOIN auctions AS a ON w.auction_id=a.auction_id AND a.cb_id > 0 AND a.category_id=1922
INNER JOIN users AS u ON w.buyer_id=u.user_id

因此，基本上，我試圖找出每個w.buyer_id關於a.cb_id涉及多少個唯一條目。

為此，我運行了上面的查詢，並得到了一行一行的結果，這很好，因為它顯示了所有唯一值； 因此我可以看到用戶A有14行（其中涉及14個唯一的CB ID），用戶B可能有5行。

因此，我想這樣做，以便獲得記錄集，輸出為：

w.buyer_id,u.username,count

我嘗試了以下方法：

SELECT DISTINCT w.buyer_id, u.username, a.cb_id, COUNT(*) AS unique_spots
FROM winners AS w
INNER JOIN auctions AS a ON w.auction_id=a.auction_id AND a.cb_id > 0 AND a.category_id=1922
INNER JOIN users AS u ON w.buyer_id=u.user_id
GROUP BY w.buyer_id
LIMIT 5000;

...但是它返回COUNT ，就好像我什至沒有對記錄集應用DISTINCT 。

我在這里做錯了什么？

Answer 1

僅編寫查詢直接執行您想要的操作怎么樣？

SELECT w.buyer_id, COUNT(DISTINCT a.cb_id)
FROM winners w INNER JOIN
     auctions a
     ON w.auction_id = a.auction_id AND a.cb_id > 0 AND
        a.category_id = 1922 INNER JOIN
     users u ON w.buyer_id = u.user_id
GROUP BY w.buyer_id;

加入users似乎是多余的：

SELECT w.buyer_id, COUNT(DISTINCT a.cb_id)
FROM winners w INNER JOIN
     auctions a
     ON w.auction_id = a.auction_id AND a.cb_id > 0 AND
        a.category_id = 1922 
GROUP BY w.buyer_id;

Answer 2

您是否嘗試過：

SELECT w.buyer_id, u.username, a.cb_id, COUNT(*) AS unique_spots
FROM winners AS w
INNER JOIN auctions AS a ON w.auction_id=a.auction_id AND a.cb_id > 0 AND a.category_id=1922
INNER JOIN users AS u ON w.buyer_id=u.user_id
GROUP BY w.buyer_id, u.username, a.cb_id
LIMIT 5000;