如何在sql中过滤空值

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),而且我过去WHERE用来过滤我的表以找出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