题解 | 统计所有课程参加培训人次
SELECT COUNT(staff_id) staff_nums
from (
SELECT DISTINCT staff_id
FROM cultivate_tb
WHERE course like '%course1%'
UNION ALL
SELECT DISTINCT staff_id
FROM cultivate_tb
WHERE course like '%course2%'
UNION ALL
SELECT DISTINCT staff_id
FROM cultivate_tb
WHERE course like '%course3%'
) t
固定次数，考虑人员即可
注意字段名称要和结果一致
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