题解 | SQL 185. 牛客直播转换率

SELECT
    b.course_id,
    b.course_name,
    ROUND(100 * SUM(if_sign) / SUM(if_vw), 2) AS `sign_rate(%)`
FROM
    behavior_tb a
    LEFT JOIN course_tb b on a.course_id = b.course_id
GROUP BY
    b.course_id,
    b.course_name
ORDER BY
    course_id ASC;