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

我有这样的查询

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

结果应该是这样的

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

我想补充的是加入表B.
如果UserID在表B中的Num中有值，我想用/ Num Grouped by Key计算UserID

这是理想的结果

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

我尝试编写子查询，但我无法将其附加到主查询。子查询是这样的。

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

如果我正确地理解了这一点，你要找的是当用户ID使用它们时表A中键的计数，然后是表B中出现的唯一用户ID数量的计数在第一个表A查询中并有一个Num。

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]

此查询提供您期望的结果。

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

OUTER APPLY

怎么样？

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

sql join如果其他表中存在值，则计算它

3 个答案: