Question

假设我有一张桌子：

    yr      mo    user   visits
    2015    11    A       3
    2015    11    A       3 
    2015    11    B       4    
    2015    11    B       4   
    2015    11    B       4
    2015    11    C       3
    2015    12    A       6
    2015    12    A       2
    2015    12    B       1
    2015    12    C       6

我需要汇总到：

     yr    mo   visitor min  max  cntmin  cntmax
    2015   11    3       3     4     2       1
    2015   12    3       1     6     1       2

其中，vistor是每月唯一身份访问者的数量，min是每月最大访问次数，max是每月最大用户数，cntmin和cnt max是最小和最大用户数（分别））。

除了cntmin和cntmax之外，我在聚合表中有所有列。我似乎无法弄清楚如何找到他们。任何帮助都将不胜感激。我正在使用tansact sql。

Answer 1

我会使用两个级别的聚合来处理这个问题：

.row {
    width: 100%;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
}

button {
    width: 200px;
}

Answer 2

尝试（旧的和不正确的）：

SELECT yr, mo, COUNT(DISTINCT user) AS visitor
   , MIN(visits) AS min 
   , MAX(visits) AS max 
   , COUNT(CASE WHEN visits = MIN(visits) THEN 1 ELSE NULL END) AS cntMin 
   , COUNT(CASE WHEN visits = MAX(visits) THEN 1 ELSE NULL END) AS cntMax
FROM TableName
GROUP BY yr, mo

新（后期建议）：

SELECT A.yr, A.mo, A.visitor, A.min, A.max
, (SELECT B.yr, B.mo, COUNT(B.visits) FROM TableName AS B WHERE B.yr = A.yr AND B.mo = A.mo AND B.visits = A.min GROUP BY B.yr, B.mo) AS cntMin
, (SELECT C.yr, C.mo, COUNT(C.visits) FROM TableName AS C WHERE C.yr = A.yr AND C.mo = A.mo AND C.visits = A.max GROUP BY C.yr, C.mo) AS cntMax
FROM 
(SELECT TableName.yr, TableName.mo, COUNT(DISTINCT TableName.user) AS visitor
   , MIN(visits) AS min 
   , MAX(visits) AS max 
FROM TableName
GROUP BY yr, mo) AS A

SQL计数最少的观察数

2 个答案: