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
    WHERE
        course IS NOT NULL
)A