select  count(*) from TM_teacherprofile where jobcategory1='专职'

select    min(sc.subjectsClassname) as subjectsClassName,
        min(s.subjectname) as subjectname,
        min(tp.jobcategory1) as jobcategory1,
        min(g.gradename) as gradename,
        count(distinct A.SubjectsClassID) as ClassCount  
        
    from BI_SubjectLessonForSalary as A
    left join
    BI_subjects s on A.subjectID=s.subjectID
    left join 
    BI_Grades g on s.gradeID=g.gradeID
    left join
    Bi_subjectsClass sc on A.subjectsClassID=sc.subjectsClassID
    left join
    Tm_TeacherProfile tp on A.teacherID=tp.ID1    
    
    where A.TeacherID is not null and A.teacherID>0 and tp.jobcategory1='专职'
group by s.subjectname  

select  min(sc.subjectsClassname) as subjectsClassName,
        min(s.subjectname) as subjectname,
        min(tp.jobcategory1) as jobcategory1,
        min(g.gradename) as gradename,
        count(distinct A.SubjectsClassID) as ClassCount,
        (select  count(*) from TM_teacherprofile where jobcategory1='专职')*100.0/
        nullif(count(distinct A.SubjectsClassID),0) as Rate
from BI_SubjectLessonForSalary as A
left join BI_subjects s on A.subjectID=s.subjectID
left join BI_Grades g on s.gradeID=g.gradeID
left join Bi_subjectsClass sc on A.subjectsClassID=sc.subjectsClassID
left join Tm_TeacherProfile tp on A.teacherID=tp.ID1     
where A.TeacherID is not null and A.teacherID>0 and tp.jobcategory1='专职'
group by s.subjectname

------解决方案--------------------
try
SQL code
select    min(sc.subjectsClassname) as subjectsClassName,
        min(s.subjectname) as subjectname,
        min(tp.jobcategory1) as jobcategory1,
        min(g.gradename) as gradename,
        -------------------------------------
        1.0*count(distinct A.SubjectsClassID)/(count(tp1.*) as ClassCount  
        -------------------------------------
        
    from BI_SubjectLessonForSalary as A
    left join
    BI_subjects s on A.subjectID=s.subjectID
    left join 
    BI_Grades g on s.gradeID=g.gradeID
    left join
    Bi_subjectsClass sc on A.subjectsClassID=sc.subjectsClassID
    left join
    Tm_TeacherProfile tp on A.teacherID=tp.ID1
    -------------------------------------------------------
    left join
    Tm_TeacherProfile tp1 on A.teacherID=tp1.ID1 and tp1.jobcategory1='专职'     
    -------------------------------------------------------
    where A.TeacherID is not null and A.teacherID>0 and tp.jobcategory1='专职'
    
group by s.subjectname

------解决方案--------------------
select    min(sc.subjectsClassname) as subjectsClassName,
       min(s.subjectname) as subjectname,
       min(tp.jobcategory1) as jobcategory1,
       min(g.gradename) as gradename,
       count(distinct A.SubjectsClassID) as ClassCount，
       count(distinct A.SubjectsClassID)/count(tp.teacherID)*1.0,--注意0的判断
     
   from BI_SubjectLessonForSalary as A
   left join
   BI_subjects s on A.subjectID=s.subjectID
   left join  
   BI_Grades g on s.gradeID=g.gradeID
   left join
   Bi_subjectsClass sc on A.subjectsClassID=sc.subjectsClassID
   left join
   Tm_TeacherProfile tp on A.teacherID=tp.ID1