题解 | 统计所有课程参加培训人次

SELECT c1_cnt+c2_cnt+c3_cnt AS staff_nums
FROM (SELECT SUM(IF(course LIKE('%1%'),1,0)) c1_cnt,
SUM(IF(course LIKE('%2%'),1,0)) c2_cnt,
SUM(IF(course LIKE('%3%'),1,0)) c3_cnt
FROM cultivate_tb
WHERE course IS NOT NULL
) AS t;

多值列：可以用LIKE关键字进行匹配