MySQL 統計兩種狀態的數量，兩個數據相除后保留四位小數

MySQL中有時需要統計兩種狀態的數量，用到的函數為count(e.status = 3 or null),兩整數相除並保留四位小數用convert（兩數相除，decimal（10,位數））

SELECT
            e.dept_id deptId,
            count( e.STATUS = 3 OR NULL ) AS status3,
            count( e.STATUS = 4 OR NULL ) AS status4,
            convert(count( e.STATUS = 4 OR NULL ) /(count( e.STATUS = 3 OR NULL )+count( e.STATUS = 4 OR NULL )),decimal(10,4)) as rectRank
        FROM
            yn_wc_event e
            LEFT JOIN sys_dept t ON e.dept_id = t.id
        WHERE
            SUBSTR( e.find_time, 1, 4 ) = DATE_FORMAT( NOW( ), '%Y' )
            AND e.STATUS IN ( '3', '4' )
        GROUP BY
            e.dept_id,
            t.`name`
        order by rectRank desc

執行結果為：

   final:不積跬步,無以至千里.不積小流,無以成江海