题解 | 统计所有课程参加培训人次

方法一：

# select
#     sum(course1) + sum(course2) + sum(course3) as staff_nums
# from
#     (
#         select
#             info_id,
#             staff_id,
#             if (course like '%1%', 1, 0) as course1,
#             if (course like '%2%', 1, 0) as course2,
#             if (course like '%3%', 1, 0) as course3
#         from
#             cultivate_tb
#     ) as t

方法二：

# 对“，” 进行判断
select sum(length(course)-length(replace(course, ',',''))+1) as staff_nums
from cultivate_tb