Question

我有一个高级查询的问题，我正在努力解决这个问题。

此时，投票表中的投票与给定的音轨相对应。我的查询需要根据已经获得的投票获得音轨的排名。

我的方法在表中有投票时效果很好，但当没有值时，等级被赋予NULL值。

以下是查询：

SELECT soundtrack.*, 
       (SELECT WrappedQuery.rank 
        FROM   (SELECT @rownum := @rownum + 1 AS rank, 
                       prequery.soundtrack_id 
                FROM   (SELECT @rownum := 0) sqlvars, 
                       (SELECT Count(*), 
                               soundtrack_id 
                        FROM   vote 
                        GROUP  BY vote.soundtrack_id 
                        ORDER  BY Count(*) DESC) prequery) WrappedQuery 
        WHERE  WrappedQuery.soundtrack_id = soundtrack.id) AS rank 
FROM   soundtrack 
WHERE  soundtrack.id = 33 
       AND live = 1 
ORDER  BY rank ASC

我觉得问题与(SELECT COUNT(*))部分有关，但到目前为止我所尝试的一切都没有用完。

希望有人可以解释我的问题。

修改这是SQLFiddle http://www.sqlfiddle.com/#!2/c8db2/2/0

Answer 1

这是一件好事：

SELECT soundtrack.*, 
(SELECT WrappedQuery.rank 
FROM   (SELECT @rownum := @rownum + 1 AS rank, 
               prequery.soundtrack_id 
        FROM   (SELECT @rownum := 0) sqlvars, 
               (
               SELECT COALESCE(COUNT(vote.soundtrack_id),0) AS no_rows, 
                       soundtrack.id AS soundtrack_id 
                FROM   soundtrack
                LEFT JOIN  vote ON soundtrack.id=vote.soundtrack_id
                GROUP  BY soundtrack.id
                ORDER  BY 1 DESC
               ) prequery) WrappedQuery 
WHERE  WrappedQuery.soundtrack_id = soundtrack.id) AS rank 
FROM   soundtrack
ORDER  BY rank ASC;

参见：http://www.sqlfiddle.com/#!2/74698/2/0

Answer 2

我使用row_number函数在我自己的工作中有一些运气排名。但除此之外，合并功能可能会帮助你。

SELECT soundtrack.*, rankquery.rank
FROM (
    SELECT row_number() over(partition by prequery.soundtrack_id order by prequery.num_votes) as rank,
    prequery.soundtrack_id
        FROM (
            SELECT COALESCE(COUNT(*),0) as num_votes, soundtrack_id
            FROM vote
            GROUP BY soundtrack_id
            ORDER BY num_votes DESC
            ) prequery
    ) rankquery
INNER JOIN soundtrack
rankquery.soundtrack_id = soundtrack.id
WHERE  soundtrack.id = 33 
       AND live = 1
ORDER BY rank

Answer 3

SELECT soundtrack.*, rankquery.rank
FROM(
    SELECT prequery.*, @rownum := @rownum + 1 AS rank 
            (
            SELECT COALESCE(Count(*),0) as num_votes, 
                   soundtrack_id 
            FROM   vote 
            GROUP BY soundtrack_id 
            ORDER BY num_votes DESC
            ) as prequery,
            (SELECT @rownum := 0) as sqlvars
    ) rankquery
INNER JOIN soundtrack
rankquery.soundtrack_id = soundtrack.id
WHERE  soundtrack.id = 33 
       AND soundtrack.live = 1
ORDER BY rankquery.rank ASC

子查询中带有空值的COUNT（）

3 个答案: