Apply "ORDER BY" on a "UNION" (Mysql)

Question

So, everything is in the title.

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 a union and ordering them. It didn't work.

I looked around like here on Stack or here developpez (!!french website). I've tried the different examples and suggestions, but no success. It seems from what I read that it's because I am working on Mysql.

Anyway, here are my attempts, and the results.

My original 2 requests:

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

This result of a list made of the result of the first select (ordered by index key) followed by the result of 2nd select ordered by index key.

Attempt 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)

The request ran, but the result was the same as the original request: result of first select (ordered by index key) followed by the results of the second request.

Attempt 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

Request ran, result same as attempt 1, but with a warning in the Mysql logic:
(this type of close has been already analysed (ORDER BY))

Attempt 3:

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

Did not run, but an error #1064 - syntax error near UNION.

Attempt 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 

Did not run, and a nice list of 6 errors. Any suggestions?

Answer 1

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

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