Question

mysql 中 if(,,)函数在sql server中如何应用

select course.*,IF(elective.course_id, count(*), 0) as amount
from course left join elective
on course.course_id = elective.course_id
group by course.course_id
其中elective和course是两个表,如何将这段mysql语句中的IF(elective.course_id, count(*), 0)用sql server语句代替

Answer 1

declare @n int
select @n=count(*) from elective;
if(@m>0)
begin
.....
end