Question

我的sql语句中有一个情况。在这个sql语句中，我一起加入了3个表（Application_Detail，Teacher_Detail和Class_Detail），，而不是我使用WHERE来过滤我的表，看看有多少老师使用过这个应用程序，我发现了以下结果。

正如您在第1条记录中所看到的，教师相关字段和类相关字段均为空。我想知道有没有办法过滤掉第一条记录，只显示2,3,4记录？因为我想只显示记录，如果在teacherId，teacherName，class或grade列中有一些值。

   teacherId teacherName   applicationName  class   grade
1. NULL      NULL         Excel            NULL     NULL
2. 5         NULL         Excel            NULL     NULL
3. NULL      NULL         Excel            A        6
4  NULL      NULL         Excel            B        2

这是我的SQL命令

SELECT
   td.teacherId,
   teacherName,
   applicationName,
   class,
   grade
FROM
   [AppUser_Detail] as aud
LEFT OUTER JOIN [Teacher_Detail] as td ON aud.teacherId = td.teacherId
LEFT OUTER JOIN [Application_Detail] as ad ON aud.applicationId = ad.applicationId
LEFT OUTER JOIN [Class_Detail] as cd ON aud.classId = cd.classId
WHERE
aud.applicationId = 6 //I filter if my application Id is 6

Answer 1

试试这个：

SELECT
   td.teacherId,
   teacherName,
   applicationName,
   class,
   grade
FROM
   [AppUser_Detail] as aud
LEFT OUTER JOIN [Teacher_Detail] as td ON aud.teacherId = td.teacherId
LEFT OUTER JOIN [Application_Detail] as ad ON aud.applicationId = ad.applicationId
LEFT OUTER JOIN [Class_Detail] as cd ON aud.classId = cd.classId
WHERE
td.teacherId is not null OR class is not null OR grade is not null

Answer 2

SELECT
   td.teacherId,
   teacherName,
   applicationName,
   class,
   grade
FROM [AppUser_Detail] as aud
LEFT OUTER JOIN [Teacher_Detail] as td ON aud.teacherId = td.teacherId
LEFT OUTER JOIN [Application_Detail] as ad ON aud.applicationId = ad.applicationId
LEFT OUTER JOIN [Class_Detail] as cd ON aud.classId = cd.classId
WHERE
aud.applicationId = 6 //I filter if my application Id is 6 
AND NOT (td.teacherId IS NULL AND class IS NULL AND grade IS NULL)

Answer 3

SELECT *
FROM (
    SELECT td.teacherId AS [TeacherID]
        ,teacherName AS [TeacherName]
        ,applicationName AS [ApplicationName]
        ,class AS [Class]
        ,grade AS [Grade]
    FROM [AppUser_Detail] AS aud
    LEFT JOIN [Teacher_Detail] AS td ON aud.teacherId = td.teacherId
    LEFT JOIN [Application_Detail] AS ad ON aud.applicationId = ad.applicationId
    LEFT JOIN [Class_Detail] AS cd ON aud.classId = cd.classId
    WHERE aud.applicationId = 6
    )
WHERE TeacherID IS NOT NULL
    OR TeacherName IS NOT NULL
    OR Grade IS NOT NULL

如何在sql中过滤空值

3 个答案: