申请"ORDER BY"在"UNION"上(MySQL的) [英] apply "ORDER BY" on a "UNION" (Mysql)

问题描述

美好的一天. 所以，每个标题都在标题中:)

Good Day. So, everythign is in the title :)

我正在寻求合并两个请求的结果，并将结果排序在一起(因为彼此之间不是一个接一个). =>我正在考虑应用工会并命令他们. 它没有用.

I am looking to merge the result of two requests and order the result together (as in not one after the other). => I was thinking of applying an union and order them. It didn't worked.

我在这里在堆栈上或在这里 developpez(!!法国网站).我尝试不同的示例和建议，但没有成功. 从我的观点看来，这是因为我正在使用Mysql.

I looked around like here on Stack or here developpez (!!french website). I try the different exemple, and suggestion, but no success. It seems from what i red that it's because I am working on Mysql.

无论如何，这是我的尝试，以及结果:

Anyway, here are my attemps, and the results:

我原来的2个请求

SELECT * FROM user_relation WHERE from_user_id = 1
List item
SELECT * FROM user_relation WHERE to_user_id = 1

此列表的结果是首先选择的结果(由索引键表示)，然后是由索引KEy排序的第二选择的结果.

this result of a list made of the result of teh frist select (odered by index key) followed by the result of 2nd select ordered by Index KEy.

尝试1:

(SELECT * FROM user_relation WHERE from_user_id = 1 ORDER BY trust_degree)
UNION
(SELECT * FROM user_relation WHERE to_user_id = 1 ORDER BY trust_degree)

请求已执行，但结果与原始请求相同:第一个选择的结果(按索引键排序)，然后是第二个请求的结果

The request ran, but teh result were teh same as orginal request: result of first select (order by index Key) followed by the results of the second request

尝试2:

(SELECT * FROM user_relation WHERE from_user_id = 1 ORDER BY trust_degree)
UNION
(SELECT * FROM user_relation WHERE to_user_id = 1 ORDER BY trust_degree)
ORDER BY trust_degree

=>请求已运行，结果为尝试1，但在Mysql逻辑中发出警告: (这种关闭类型已经过分析(ORDER BY))

=> request ran, result as attempt 1, but with a warning i the Mysql logic: (this type of close has been already analyzed (ORDER BY))

尝试3

(SELECT * FROM user_relation WHERE from_user_id = 1
UNION
SELECT * FROM user_relation WHERE to_user_id = 1)
ORDER BY trust_degree

=>不运行，但出现错误#1064-UNION附近的语法错误

=> Do not ran, but an error #1064 - syntax error near UNION

尝试4:

SELECT *
FROM (
(SELECT * FROM user_relation WHERE from_user_id = 1)
UNION
(SELECT * FROM user_relation WHERE to_user_id = 1)
)
ORDER BY trust_degree 

=>不运行，并且列出了6条错误. 有什么建议吗?

=> do not ran, and a nice list of 6 error. Any suggestion?

推荐答案

SELECT *
FROM (
(SELECT * FROM user_relation WHERE from_user_id = 1)
UNION
(SELECT * FROM user_relation WHERE to_user_id = 1)
) AS i
ORDER BY trust_degree

您必须为您的选择分配一个别名.但是在这种情况下，UNION不是必需的，可以用简单的OR代替，正如@Karoly Horvath在其评论中指出的那样.结果查询如下:

You have to assign an alias to your select. But in this case a UNION is not necessary and could be replaced by a simple OR, as @Karoly Horvath points out in his comment. The resulting query would look like this:

SELECT 
 * 
FROM user_relation 
WHERE from_user_id = 1 OR to_user_id = 1 
ORDER BY trust_degree

这篇关于申请"ORDER BY"在"UNION"上(MySQL的)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！