SQL问题与拥有

我正在努力解决这个问题

返回一个列出语言和讲者数量的表，但只包括讲者人数>20000000的语言？根据发言者的数量将这些结果从高到低排序

这是我的代码：

SELECT 
    Language,
    Percentage / 100 AS 'Percentage',
    SUM(Population) AS Population,
    Population * Percentage AS 'Speakers'
FROM 
    language
GROUP BY 
    Language
HAVING 
    Speakers > 200000000;

---

有人能帮我吗？

你可以在下面使用演讲者的计算表达式来尝试

SELECT 
     Language,
     Percentage/100 AS 'Percentage',
     SUM(Population) AS Population,
     SUM(Population)*(Percentage/100) AS 'Speakers'
FROM language
GROUP BY Language
HAVING SUM(Population)*(Percentage/100)> 200000000
ORDER BY SUM(Population)*(Percentage/100) DESC

---

不要对列别名使用单引号。那真是个坏习惯。仅对字符串和日期常量使用单引号

SQL（一般情况下）允许您按的顺序引用列别名。有些数据库也允许您在

HAVING

子句中引用它们，但不是全部

我不确定百分比应该做什么。它应该在

组中。在其他情况下，
百分比
应作为聚合计算的一部分：

SELECT Language,
       SUM(Percentage * Population / 100) / SUM(Population) AS Percentage,
       SUM(Population) AS Population,
       SUM(Population * Percentage/100) AS Speakers
FROM language
GROUP BY Language
HAVING SUM(Population*Percentage/100.0) > 200000000
ORDER BY Speakers DESC;

请注意，有些数据库进行整数除法，因此99/100=0，而不是0.99。因此，我会：

SELECT Language, 
       SUM(Percentage * Population / 100.0) / SUM(Population) AS Percentage,
       SUM(Population) AS Population,
       SUM(Population*Percentage/100.0) AS Speakers
FROM language
GROUP BY Language
HAVING SUM(Population*Percentage/100.0) > 200000000
ORDER BY Speakers DESC;