我该如何解决我的Oracle 11G SQL查询问题？

Question

我不明白我在做什么我的问题在这里。

SELECT ORDER#, SUM(PAIDEACH * QUANTITY) AS TOTAL 
    FROM ORDERITEMS 
    WHERE TOTAL > 39.9 
    GROUP BY ORDER# 
    ORDER BY TOTAL DESC; 

这是我不断收到错误：

"TOTAL": invalid identifier 

Answer 1

既然你想对你的聚合函数有一个谓词，你可以使用HAVING子句

SELECT ORDER#, SUM(PAIDEACH * QUANTITY) AS TOTAL 
    FROM ORDERITEMS 
GROUP BY ORDER# 
HAVING SUM(PAIDEACH * QUANTITY) > 39.9 
ORDER BY TOTAL DESC; 

Answer 2

如果你想使用别名在WHERE条款，那么你可以把另一个SELECT内查询：

SELECT * 
FROM 
(
    SELECT ORDER#, SUM(PAIDEACH * QUANTITY) AS TOTAL 
    FROM ORDERITEMS 
    GROUP BY ORDER# 
) x 
WHERE x.TOTAL > 39.9 
ORDER BY x.TOTAL DESC; 

Answer 3

order by 2 desc（以列数字的引用从1开始）

有没有必要写嵌套查询，甚至把一个having子句查询。请参阅带数字的列，但不要忘记在更改查询时更改它;-)