SQL连接再算上它

Question

我有以下表格。

表A

 UserID | key
 1  | A
 2  | B
 3  | A
 4  | C
 5  | 

表B

UserID | Num
1  | 50
1  | 300
2  |
3  | 100
4  | 20

我有这样

SELECT COUNT(key) AS cnt, key 
FROM A 
WHERE key <> '' 
GROUP BY key 
ORDER BY cnt DESC 

结果查询应该是这样的

 key | cnt
 A | 2
 B | 1
 C | 1

我想补充的是加入表B.
如果用户名在num表B值，我想指望用户名与/民者皆

这里是理想的结果

 key | cnt | Has Num?
 A | 2 | 2
 B | 1 | 0
 C | 1 | 1

分组

我试着写子查询，但我不能将它连接到主查询。子查询就是这样的。

SELECT COUNT(DISTINCT UserID) AS num 
FROM B 
LEFT OUTER JOIN A ON B.UserID = A.UserID 
WHERE Num <>'' AND key <> '' 
GROUP BY key 

Answer 1

如果我正确认识这一点，你要找的是什么的计数表A中的键被用户ID使用时，然后是表B中唯一的用户ID数量都出现在第一个表A查询中的计数和有一个数字。

试试这个：

SELECT a.[Key], COUNT(a.[Key]) AS cnt, isNull(SUM(b.bCnt), 0) AS [Has Num?] 
FROM #TableA a 
LEFT OUTER JOIN (
    SELECT b.UserID, 1 
    FROM #TableB b 
    WHERE LEN(b.Num) > 0 
    GROUP BY b.UserID 
) b (UserID, bCnt) ON b.UserID = a.UserID 
WHERE LEN(a.[Key]) > 0 
GROUP BY a.[Key] 

此查询给出了您所期望的结果。

Answer 2

DECLARE @TableA TABLE(UserID INT, [Key] CHAR(1)) 
INSERT INTO @TableA VALUES(1,'A'),(2,'B'),(3,'A'),(4,'C'),(5,'') 

DECLARE @TableB TABLE(UserID INT, Num INT NULL) 
INSERT INTO @TableB VALUES(1,50),(1,300),(2,NULL),(3,100),(4,20) 


SELECT x.[Key],x.Cnt,y.[Has Num?] 
FROM 
    ( SELECT [Key],Cnt = COUNT([Key]) 
     FROM @TableA 
     WHERE LEN([Key])>0 
     GROUP BY [Key] 
    )X 
JOIN 
    (
     SELECT a.[Key],[Has Num?] = COUNT(b.Num) 
     FROM @TableA a 
     JOIN @TableB b ON a.UserID = b.UserID 
     GROUP BY a.[Key] 
    )Y 
ON x.[Key] = Y.[Key] 


Key Cnt Has Num? 
A 2 3 
B 1 0 
C 1 1 

Answer 3

怎么样的OUTER APPLY

SELECT [Key], COUNT(a.[Key]) AS cnt, SUM(x.NumCount) AS [Has Num?]  
FROM @TableA a 
OUTER APPLY (SELECT COUNT(NUM) AS NumCount 
      FROM @TableB b 
      WHERE b.UserId = a.UserId AND Num IS NOT NULL 
      ) x 
WHERE [Key] <> '' 
GROUP BY [Key] 
ORDER BY cnt DESC 

结果：

Key cnt   Has Num? 
---- ----------- ----------- 
A 2   3 
B 1   0 
C 1   1