[英]Select count of rows with unique values
我有一張桌子,里面有我們賣的所有物品。 訂單中可能有多個商品。
我想找到最受歡迎的項目顏色組合,其中訂單僅包含1個項目。 我想知道是否可以在一個MySQL語句中找到它(可能使用嵌套的Selects)。 到目前為止,我已經嘗試了幾件事但沒有成功。
ProductName | Color | OrderNum |
--------------------------------
productA | black | 1
productA | black | 1
productA | black | 2
productA | black | 3
productA | black | 4
productA | black | 4
productA | black | 5
所以“
SELECT COUNT(ProductName), ProductName WHERE ~~COUNT(OrderNum)=1~~ GROUP BY ProductName, Color
會顯示:
COUNT(ProductName) | ProductName | Color
3 | ProductA | black
實際上我有很多產品和50多種顏色。
我嘗試過的:
SELECT COUNT(ProductName), ProductName,Color,
(SELECT COUNT(OrderNum) FROM Items GROUP BY OrderNum) AS itemcount
FROM Items WHERE 1
GROUP BY ProductName,Color HAVING itemcount = 1
SELECT COUNT( ProductName ) , ProductName, Color
FROM Items
WHERE (SELECT COUNT( OrderNum ) AS itemcounts
FROM Items GROUP BY OrderNum
) =1
GROUP BY ProductName
- “子查詢返回超過1行”
謝謝你的幫助。
查詢:
SELECT
COUNT(*) as count, i.ProductName, i.Color
FROM ITems i
WHERE 1 = (SELECT COUNT( OrderNum ) AS itemcounts
FROM Items
WHERE OrderNum = i.OrderNum
)
GROUP BY ProductName, Color
結果:
| COUNT | PRODUCTNAME | COLOR |
-------------------------------
| 3 | productA | black |
嘗試這個:
SELECT ProductName, color, COUNT(ProductName)
FROM (SELECT ProductName, color, orderNum FROM Items
GROUP BY ProductName, orderNum HAVING COUNT(orderNum)=1) AS A
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