题解 | #统计所有课程参加培训人次#

select sum(num) staff_nums from (select count(*)  num from cultivate_tb 
where course like  ('%course1%')
union all 
select count(*)  num from cultivate_tb 
where course like  ('%course2%')
union  all 
select count(*)  num  from cultivate_tb 
where course like  ('%course3%')
) a