ORDER BY别名不起作用

Question

更新问题:

ERROR:  column "Fruits" does not exist

运行Postgres 7.4(是的,我们正在升级)

为什么我不能按列别名进行排序？想要在ORDER BY中使用"TypeOfFruits",为什么？

SELECT (CASE
    WHEN tof."TypeOfFruits" = 'A' THEN 'Apple' 
    WHEN tof."TypeOfFruits" = 'P' THEN 'Pear' 
    WHEN tof."TypeOfFruits" = 'G' THEN 'Grapes' 
    ELSE 'Other' END) AS "Fruits",
    SUM(CASE WHEN r.order_date 
        BETWEEN DATE_TRUNC('DAY', LOCALTIMESTAMP) AND DATE_TRUNC('DAY', LOCALTIMESTAMP) + INTERVAL '1 DAY' 
        THEN 1 ELSE 0 END) AS daily, 
    SUM(CASE WHEN r.order_date 
        BETWEEN DATE_TRUNC('MONTH', LOCALTIMESTAMP) AND DATE_TRUNC('MONTH', LOCALTIMESTAMP) + INTERVAL '1 MONTH' 
        THEN 1 ELSE 0 END) AS monthly, 
    SUM(CASE WHEN r.order_date 
        BETWEEN DATE_TRUNC('YEAR', LOCALTIMESTAMP) AND DATE_TRUNC('YEAR', LOCALTIMESTAMP) + INTERVAL '1 YEAR' 
        THEN 1 ELSE 0 END) AS yearly, 
    SUM(CASE WHEN r.order_date >= '01-01-2011 00:00:00' THEN 1 ELSE 0 END) AS lifetime 
FROM reports AS r, "TypeOfFruits" AS tof 
WHERE r.id = tof."ID" 
GROUP BY "Fruits"
ORDER BY CASE 
    WHEN "Fruits" = 'Apple' THEN 1 
    WHEN "Fruits" = 'Pear' THEN 2 
    WHEN "Fruits" = 'Grapes' THEN 3 
    ELSE 4 
END

截至目前的结果

Fruits;daily;monthly;yearly;lifetime
"Apple";17;1174;3136;3136
"Pear";28;94;94;94
"Grapes";0;191;490;490
"Other";0;2;27;27
"Other";0;0;1;1
"Other";0;0;27;27
"Other";0;6;28;28
"Other";0;58;229;229
"Other";0;3;3;3
"Other";0;0;1;1

期望的结果将是具有"其他"总计的一行,因此总共四行(x将是总计)

Fruits;daily;monthly;yearly;lifetime
"Apple";17;1174;3136;3136
"Pear";28;94;94;94
"Grapes";0;191;490;490
"Other";x;x;x;x

Answer 1

您可以使用ORDER BY 1第一个字段来订购,即"Fruits".同样有效GROUP BY

更新

对于订单,而不是case在中order by,在...中创建一个新列说...第二个位置:

(CASE 
    WHEN "Fruits" = 'Apple' THEN 1 
    WHEN "Fruits" = 'Pear' THEN 2 
    WHEN "Fruits" = 'Grapes' THEN 3 
    ELSE 4 ) as Order

然后在你ORDER BY 2.

Answer 2

原因可以在文档中找到:

每个表达式[在ORDER BY列表中]可以是输出列的名称或序号(SELECT列表项),也可以是由input -column值组成的任意表达式.

(我的重点)

原因是旧版本的SQL标准(SQL-92)只允许按输出列名称或编号进行排序,而较新版本允许按任意表达式排序,但这些表达式是由输入列值组成的.

其他答案已包含适用于您的案例的各种合适的解决方法.