需要有关 LIMIT 子查询的帮助

Question

我需要用户 ID = x 的每个标准 ID 的最后三个分数和总分。一旦我得到了这个，我就会找出每个分数/总分的百分比。然后我对百分比进行平均，这个百分比是该标准 id 的最终百分比。我遇到的问题是试图为每个标准 id 输出最终百分比。我可以做一个但不确定如何构建查询来执行其余的行。

获取单个标准 ID 的结果

SELECT sto_standard_id, avg((sto_count / sto_total) * 100)
FROM (
SELECT so.sto_standard_id,so.sto_count ,so.sto_total  
FROM mydb.sto_stat_overall as so 
WHERE sto_user_id = 1 
AND so.sto_standard_id = 4
ORDER BY sto_id 
DESC LIMIT 3) as sub

这有效，

我尝试进行相同的尝试，但对多个标准 ID 有效。

SELECT sto_standard_id, avg((sto_count / sto_total) * 100)
FROM (
SELECT so.sto_standard_id,so.sto_count ,so.sto_total  
FROM mydb.sto_stat_overall as so 
WHERE so.sto_standard_id IN (SELECT DISTINCT sto_standard_id FROM mydb.sto_stat_overall WHERE sto_user_id = 1)
ORDER BY sto_id 
DESC LIMIT 3) as sub

它仍然只有 returns 一行。

这里有一些数据可以玩。

    DROP TABLE IF EXISTS `sto_stat_overall`;
    /*!40101 SET @saved_cs_client     = @@character_set_client */;
    /*!40101 SET character_set_client = utf8 */;
    CREATE TABLE `sto_stat_overall` (
      `sto_id` bigint(20) NOT NULL AUTO_INCREMENT,

  `sto_transaction_id` bigint(20) DEFAULT NULL,
  `sto_user_id` bigint(20) unsigned NOT NULL,
  `sto_standard_id` bigint(20) DEFAULT NULL,
  `sto_count` mediumint(9) DEFAULT NULL,
  `sto_total` mediumint(9) DEFAULT NULL,
  PRIMARY KEY (`sto_id`),
  KEY `transaction_id` (`sto_transaction_id`),
  KEY `user_standard` (`sto_user_id`,`sto_standard_id`)
) ENGINE=InnoDB AUTO_INCREMENT=19 DEFAULT CHARSET=utf8;

LOCK TABLES `sto_stat_overall` WRITE;
/*!40000 ALTER TABLE `sto_stat_overall` DISABLE KEYS */;
INSERT INTO `sto_stat_overall` VALUES (1,1,1,1,1,1),(2,1,1,2,0,1),(3,2,1,3,1,2),(4,2,1,4,0,2),(5,10,1,6,1,1),(6,10,1,4,0,1),(7,10,1,119,0,1),(8,10,1,3,1,1),(9,10,1,1,1,1),(10,11,1,4,1,1),(11,11,1,10,0,1),(12,11,1,3,0,1),(13,11,1,1,1,1),(14,11,1,119,0,1),(15,32,1,1,1,1),(16,32,1,2,0,1),(17,33,1,1,1,1),(18,33,1,2,0,1);

Answer 1

select sto_standard_id, avg((sto_count / sto_total) * 100) from (
select @rank:=if(@prev_cat=sto_standard_id ,@rank+1,1) as rank
  ,so.sto_standard_id,so.sto_count ,so.sto_total,
  @prev_cat:=sto_standard_id 

from sto_stat_overall so,(select @rank:=0, @prev_cat:="")t
  WHERE sto_user_id = 1
order by sto_standard_id , sto_id  desc
  ) temp
  where temp.rank<=3
  group by sto_standard_id

需要有关 LIMIT 子查询的帮助

Need help on subqueries with LIMIT

mysql

subquery