不，你不能任意地限制子查询(你可以在较新的mysql中有限地这样做，但不能每组5个结果)。

这是一个分组最大类型查询，在SQL中执行起来并不简单。在某些情况下，有很多更有效的方法来解决这个问题，但对于一般的top-n，你会想看看Bill对前面一个类似问题的答案。

与此问题的大多数解决方案一样，如果有多行具有相同的速率值，它可以返回超过5行，因此您可能仍然需要大量的后处理来检查这一点。

下面的post: sql:每组选择前N条记录描述了在没有子查询的情况下实现这一目标的复杂方法。

它改进了这里提供的其他解决方案:

在单个查询中执行所有操作 能够正确地利用索引 避免子查询，众所周知，在MySQL中会产生糟糕的执行计划

然而，它并不漂亮。如果在MySQL中启用窗口函数(又名分析函数)，就可以实现一个很好的解决方案——但它们没有。 文章中使用的技巧利用了GROUP_CONCAT，它有时被描述为“穷人的MySQL窗口函数”。

构建虚拟列(如Oracle中的RowID)

表:

CREATE TABLE `stack` 
(`year` int(11) DEFAULT NULL,
`id` varchar(10) DEFAULT NULL,
`rate` float DEFAULT NULL) 
ENGINE=InnoDB DEFAULT CHARSET=utf8mb4

数据:

insert into stack values(2006,'p01',8);
insert into stack values(2001,'p01',5.9);
insert into stack values(2007,'p01',5.3);
insert into stack values(2009,'p01',4.4);
insert into stack values(2001,'p02',12.5);
insert into stack values(2004,'p02',12.4);
insert into stack values(2005,'p01',2.1);
insert into stack values(2000,'p01',0.8);
insert into stack values(2002,'p02',12.2);
insert into stack values(2002,'p01',3.9);
insert into stack values(2004,'p01',3.5);
insert into stack values(2003,'p02',10.3);
insert into stack values(2000,'p02',8.7);
insert into stack values(2006,'p02',4.6);
insert into stack values(2007,'p02',3.3);
insert into stack values(2003,'p01',7.4);
insert into stack values(2008,'p01',6.8);

SQL是这样的:

select t3.year,t3.id,t3.rate 
from (select t1.*, (select count(*) from stack t2 where t1.rate<=t2.rate and t1.id=t2.id) as rownum from stack t1) t3 
where rownum <=3 order by id,rate DESC;

如果删除t3中的where子句，则如下所示:

GET "TOP N Record"——>在where子句(t3的where子句)中添加rownum <=3;

选择“年份”——>在where子句中增加BETWEEN 2000 AND 2009 (t3的where子句);

对于那些像我一样有查询超时的人。我做了下面的限制和任何其他由特定的组。

DELIMITER $$
CREATE PROCEDURE count_limit200()
BEGIN
    DECLARE a INT Default 0;
    DECLARE stop_loop INT Default 0;
    DECLARE domain_val VARCHAR(250);
    DECLARE domain_list CURSOR FOR SELECT DISTINCT domain FROM db.one;

    OPEN domain_list;

    SELECT COUNT(DISTINCT(domain)) INTO stop_loop 
    FROM db.one;
    -- BEGIN LOOP
    loop_thru_domains: LOOP
        FETCH domain_list INTO domain_val;
        SET a=a+1;

        INSERT INTO db.two(book,artist,title,title_count,last_updated) 
        SELECT * FROM 
        (
            SELECT book,artist,title,COUNT(ObjectKey) AS titleCount, NOW() 
            FROM db.one 
            WHERE book = domain_val
            GROUP BY artist,title
            ORDER BY book,titleCount DESC
            LIMIT 200
        ) a ON DUPLICATE KEY UPDATE title_count = titleCount, last_updated = NOW();

        IF a = stop_loop THEN
            LEAVE loop_thru_domain;
        END IF;
    END LOOP loop_thru_domain;
END $$

它循环遍历一个域列表，然后每个域只插入200个限制

试试这个:

SET @num := 0, @type := '';
SELECT `year`, `id`, `rate`,
    @num := if(@type = `id`, @num + 1, 1) AS `row_number`,
    @type := `id` AS `dummy`
FROM (
    SELECT *
    FROM `h`
    WHERE (
        `year` BETWEEN '2000' AND '2009'
        AND `id` IN (SELECT `rid` FROM `table2`) AS `temp_rid`
    )
    ORDER BY `id`
) AS `temph`
GROUP BY `year`, `id`, `rate`
HAVING `row_number`<='5'
ORDER BY `id`, `rate DESC;

试试这个:

SELECT h.year, h.id, h.rate 
FROM (SELECT h.year, h.id, h.rate, IF(@lastid = (@lastid:=h.id), @index:=@index+1, @index:=0) indx 
      FROM (SELECT h.year, h.id, h.rate 
            FROM h
            WHERE h.year BETWEEN 2000 AND 2009 AND id IN (SELECT rid FROM table2)
            GROUP BY id, h.year
            ORDER BY id, rate DESC
            ) h, (SELECT @lastid:='', @index:=0) AS a
    ) h 
WHERE h.indx <= 5;