题解 | #统计所有课程参加培训人次#

SELECT SUM(CAST(course_number AS UNSIGNED)) AS staff_nums
FROM(
SELECT 
CASE
WHEN course LIKE'course_,course_,course_' THEN '3'
WHEN course LIKE'course_,course_' THEN '2'
WHEN course LIKE'course_' THEN '1'
ELSE null END AS course_number
FROM cultivate_tb
) a