Question

我需要一些关于MySQL SELECT语句的帮助。不幸的是，此声明无法正常工作。它似乎根据学校名称的字母顺序排名，而不是reading_percent_proficient_and_advanced。我该如何解决？

SET @rank=0;
SELECT @rank:=@rank+1 as rank, 
       sy.formatted_school_name, 
       FLOOR(d.reading_percent_proficient + d.reading_percent_advanced) AS reading_percent_proficient_and_advanced 
FROM d_test_scores AS d, 
       sy_2010_2011_school_type AS sy  
WHERE sy.school_id = d.school_id 
       AND sy.school_group = 'public school'
       AND sy.school_type ='elementary' 
ORDER BY reading_percent_proficient_and_advanced DESC

如果我取消加入，那么这句话给了我正确的排名（但我当时没有学校名称）：

SET @rank=0;
SELECT @rank:=@rank+1 as rank,  
       d.school_id, 
       FLOOR(d.reading_percent_proficient + d.reading_percent_advanced) AS reading_percent_proficient_and_advanced  
FROM d_test_scores AS d 
ORDER BY reading_percent_proficient_and_advanced DESC;

我的加入有什么问题？

Answer 1

（推测）我相信在强制执行ORDER BY排序之前计算排名。在原始查询中，恰好在ORDER BY之前按照您想要的顺序返回结果，从而排名正确，在高级查询中，结果最初以不同的顺序返回。

尝试将排名添加到学校名称和熟练程度等级的已订购集（子查询）中。

Answer 2

我实际上没有看到任何JOIN关键字，试试这个吗？

SET @rank=0;
SELECT @rank:=@rank+1 as rank, 
       sy.formatted_school_name, 
       FLOOR(d.reading_percent_proficient + d.reading_percent_advanced) AS reading_percent_proficient_and_advanced 
FROM d_test_scores d JOIN sy_2010_2011_school_type sy on sy.school_id = d.school_id 
WHERE  sy.school_group = 'public school'
       AND sy.school_type ='elementary' 
ORDER BY reading_percent_proficient_and_advanced DESC

只是一个猜测。

MySQL加入的问题

2 个答案: