Inner queries on the same table - is there a better way? - sql

Question

I have these two tables (simplified versions)
Orders
owner_id | user_1 | user_2 | amount | order_id
-----------------------------------------------
1 | 2 | 3 | 100 | AAA
1 | 7 | 2 | 200 | BBB
2 | 3 | 5 | 400 | CCC
Users
user_id | username
------------------
1 | John
2 | Robert
3 | Sally
4 | Mario
5 | Albert
6 | Hernest
7 | Homer
I need to get, in one query, all the info related to a particular order, including the owner_id, user_1, user_2 usernames.
The result I'm trying to achieve is the following:
owner_id | owner_username | user_1_id | user_1_username | user_2_id | user_2_username | order_total
----------------------------------------------------------------------------------------------------
1 | John | 2 | Robert | 3 | Sally | 100
So far I'm getting all I need with a query like this:
SELECT o.owner_id AS owner_id, (SELECT username FROM Users where user_id = 1) AS owner_username,
o.user_1 AS user_1_id, (SELECT username FROM Users where user_id = 2) AS user_1_username,
o.user_2 AS user_2_id, (SELECT username FROM Users where user_id = 3) AS user_2_username,
o.amount AS order_total
FROM Orders.o
WHERE o.order_id = 'AAA'
This is an example to retrieve the info for the first order.
I'm not very satisfied by the inner queries I have to do to get each username, I think it's kinda ugly.
Is there a more elegant or more performant way to get the usernames?
Thank you

Answer 1

This may help
SELECT od.*,
U1.username AS 'User_1_Name',
U2.username AS 'User_2_Name',
U3.username AS 'User_3_Name'
FROM Orders od
LEFT OUTER JOIN Users U1
ON od.Owner_Id = U1.User_Id
LEFT OUTER JOIN Users U2
ON od.User_1 = U2.User_Id
LEFT OUTER JOIN Users U3
ON od.User_2 = U3.User_Id
WHERE order_id = 'AAA'