题解 | 请写出计算粉丝ctr的sql语句

SELECT
    ROUND(
        SUM(c.read_num) / SUM(c.show_num)
        ,4) AS fans_ctr
FROM a
INNER JOIN b
    ON (a.author_id = b.author_id)
INNER JOIN c
    ON (b.content_id = c.content_id
        AND a.fans_id = c.fans_id);