SQL：使用不同的子句获取Column表两次

Question

我尝试使用不同的子句两次在同一个表中获取相同的列：

我的查询：

SELECT 
    * 
FROM
    (SELECT TOP 10 
         CONVERT(DATE, attemptdate) AS Date, 
         Max(currentcount) AS A 
     FROM   
         logintracking 
     INNER JOIN 
         maxuser ON logintracking.loginid = maxuser.loginid 
     INNER JOIN 
         site ON site.siteid = maxuser.defsite 
     WHERE  
         attemptdate BETWEEN @dateDebut AND @dateFin 
         AND logintracking.clientaddr IN ('10.118.254.21', '10.118.254.156') 
     GROUP BY 
         CONVERT(DATE, attemptdate) 
     ORDER BY 
         CONVERT(DATE, attemptdate) ASC
    ) AS T1, 
    (SELECT TOP 10 
         CONVERT(DATE, attemptdate) AS Date, 
         MAX(currentcount) AS B 
     FROM   
         logintracking 
     INNER JOIN 
         maxuser ON logintracking.loginid = maxuser.loginid 
     INNER JOIN 
         site ON site.siteid = maxuser.defsite 
     WHERE  
         attemptdate BETWEEN @dateDebut AND @dateFin 
         AND logintracking.clientaddr = '10.118.254.35' 
     GROUP BY 
         CONVERT(DATE, attemptdate) 
     ORDER BY 
         CONVERT(DATE, attemptdate) ASC) AS T2 

结果：

期望的结果：

我的目标是两次获取相同的列'max（currentcount）'并应用不同的where子句，以便得到两个名为（A和B）的列，我还需要在第一列显示日期，你能帮忙吗？ ？谢谢

Answer 1

由于A和B之间的唯一区别是logintracking.clientaddr，你可以将该条件置于CASE函数中的MAX语句中：

SELECT CONVERT(DATE, attemptdate) AS Date, 
    MAX(CASE WHEN logintracking.clientaddr IN ( '10.118.254.21', '10.118.254.156' ) THEN currentcount END) AS A,
    MAX(CASE WHEN logintracking.clientaddr IN ( '10.118.254.35' ) THEN currentcount END) AS B
FROM logintracking 
    INNER JOIN maxuser 
        ON logintracking.loginid = maxuser.loginid 
    INNER JOIN site 
        ON site.siteid = maxuser.defsite 
WHERE attemptdate BETWEEN @dateDebut AND @dateFin
GROUP BY CONVERT(DATE, attemptdate) 
ORDER BY CONVERT(DATE, attemptdate) ASC