在查询

Question

我有以下查询，我想要排除'否'的值。我想要包含N / A，Yes和null。 '否'，'是'，'N / A'和'null'是此列中的唯一值。当我运行我的查询时，它不返回空值，但它确实返回'N / A'和'是'。

select s.schoolid as "School Code", 
       sch.name as "School Name", 
       s.student_number as "Student Id", 
       s.lastfirst as "Name", 
       s.gender as "Gender", 
       s.grade_level as "Grade", 
       s.street as "Street", 
       s.city as "City", 
       s.state as "State", 
       s.zip as "Zip", 
       s.home_phone as "Home Phone" 
from u_students u 
  left join students s on u.studentsdcid = s.dcid
  left join schools sch on s.schoolid = sch.school_number
where s.grade_level in ('11','12')
  and s.enroll_status = '0'
  and U.Scs_Perm_Share_Military Not like 'No'
order by sch.name asc ;

Answer 1

如果SELECT语句要测试除其他值之外的空值，则它必须包含IS NULL子句。另外，正如其他人所说，你应该使用左连接条件，而不是在where子句中放置过滤器：

select s.schoolid as "School Code", 
       sch.name as "School Name", 
       s.student_number as "Student Id", 
       s.lastfirst as "Name", 
       s.gender as "Gender", 
       s.grade_level as "Grade", 
       s.street as "Street", 
       s.city as "City", 
       s.state as "State", 
       s.zip as "Zip", 
       s.home_phone as "Home Phone" 
from u_students u 
  left join students s on u.studentsdcid = s.dcid
                      and s.grade_level in ('11','12')
                      and s.enroll_status = '0'
  left join schools sch on s.schoolid = sch.school_number
where (U.Scs_Perm_Share_Military IS NULL
       OR
       U.Scs_Perm_Share_Military <> 'No'
      )
order by sch.name asc ;