關於mysql 自定義@row的使用

• 應用場景:在對成績或者積分排名時,往往需要顯示排名;

  • 成績排名:相同分數的人,名次相同

    Select s.Score,
        case 
          when @rowtotal = s.Score then cast(@rownum as SIGNED  INTEGER) # 當這個成績和@rowtotal上一次的成績相同時,@rownum不變
          when @rowtotal := s.Score then cast(@rownum :=@rownum +1 as SIGNED  INTEGER) # 當取到的成績和上一次成績不同時, @rownum +1 ,rank排名加一
          when @rowtotal = 0 then cast(@rownum :=@rownum +1 as SIGNED  INTEGER) # 當取到的成績為0時,排名+1
        end as Rank 
    from 
    (select Id,Score from Scores order by Score desc)s, # 通過分數倒序排列成績
    (Select @rownum :=0,@rowtotal :=null) r	#這個是關鍵,@rownum,@rowtotal先置空,然后和上邊的成績關聯
    

  • 積分排名:按積分插入時間排名

    SELECT
        obj.score,@rownum := @rownum + 1 AS Rank
    FROM
        (
            SELECT
                user_id,
                score
            FROM
                `sql_rank`
            ORDER BY
                score DESC,
                update_time ASC
        ) AS obj,
        (SELECT @rownum := 0) r
    

    我遇到的問題是,排名顯示的是1.0,2.0的double類型,所以我用cast(@rownum as SIGNED INTEGER)轉化了一下