题解 | 统计所有课程参加培训人次

select sum(t1) staff_nums
from (select 
case when course is NULL then 0 else length(course)-length(replace(course,",",""))+1 end t1
from cultivate_tb) t2

SELECT SUM( CASE WHEN course IS NULL THEN 0 ELSE LENGTH(course) - LENGTH(REPLACE(course, ',', '')) + 1 END ) AS staff_nums FROM cultivate_tb;

LENGTH(course) - LENGTH(REPLACE(course, ',', '')) + 1// 原字符长度-提取逗号后字符串长度+1