在SQL查詢中選擇帶有連接的計數

Question

如何通過查詢檢查a，b，c，d分別添加了多少個產品？

表格1

admin_id admin_name
3           a
4           b
5           c  
6           d

表2

admin_id products
3          pDeal
3          pSeal    
4          pAeal
5          pZeal
6          pXeal    
3          pHeal
6          pPeal

Answer 1

您需要一個簡單的JOIN和一個COUNT查詢：

SELECT table1.admin_name, COUNT(*) as cnt
FROM
  table1 INNER JOIN table2
  ON table1.admin_id = table2.admin_id
GROUP BY
  table1.admin_name

Answer 2

嘗試這個...

    SELECT a.admin_name, COUNT(b.products) as 'CountOfProducts' 
    FROM table1 a INNER JOIN table2 b ON a.admin_id = b.admin_id
    GROUP BY a.admin_name

Answer 3

用這個

SELECT adm.admin_name,COUNT(pdr.products) as ProductCnt 
FROM table1 AS adm 
JOIN table2 AS pdr 
  ON adm.admin_id = pdr.admin_id 
GROUP BY adm.admin_id;

Answer 4

SELECT t1.admin_name, COUNT(t2.products)
FROM table1 AS t1 LEFT JOIN table2 AS t2 ON t1.admin_id = t2.admin_id
WHERE 1
GROUP BY t2.admin_id

LEFT JOIN將確保table2的表1的某些管理員沒有任何記錄的情況。

Answer 5

您可以像這樣使用內部選擇：

SELECT 
    table1.admin_name, 
    (SELECT COUNT(*) 
     FROM table2 
     WHERE table1.admin_id = table2.admin_id) As cnt
FROM
  table1;