How to combine two different SQL queries in one SQL statement? - sql

Question

I have two tables which are:
Members
Member_id | Member_user_name | Member_account_id
and
Members_transaction
Member_id (sender) | Member_transaction_id | Member_account_id (recipient) | Amount | from_to
All columns have data but from_to is a new column added. I would like to add the username of sender or recipient into the column from_to.
I had use below SQL query to find out the sender's or recipient's username:
select member_user_name member_involved
from Members_transaction
left
join members
on members_transaction.member_account_id = members.member_account_id
I want to add the SQL query in this SQL query:
SELECT member_transaction_id
, mp.member_account_id
, m.member_user_name
, amount
, CASE
-- when the amount starts with "-" such as "-100" it means paid to recipient
WHEN amount LIKE '-%' THEN 'Paid to' + member_involved
-- else it is received from the sender
ELSE ' Received from '+ member_involved
END AS from_to
FROM members_transaction MP (nolock)
LEFT
JOIN members M (NOLOCK)
ON M.MEMBER_ID = MP.MEMBER_ID
AND M.IS_USE = 1
WHERE MP.IS_USE = 1
Since the condition is different (the ON), how can i combine the SQL query of finding sender or recipient into the below SQL query?

Answer 1

You can join twice with members, once for the sender name, once for the receiver name:
SELECT member_transaction_id
, mp.member_account_id
, m.member_user_name
, amount
, CASE
-- when the amount starts with "-" such as "-100" it means paid to recipient
WHEN amount LIKE '-%' THEN 'Paid to' + M2.member_user_name
-- else it is received from the sender
ELSE ' Received from '+ M.member_user_name
END AS from_to
FROM members_transaction MP (nolock)
LEFT JOIN members M (NOLOCK) ON M.MEMBER_ID = MP.MEMBER_ID AND M.IS_USE = 1
LEFT JOIN members M2 (NOLOCK) ON M2.member_account_id = MP.member_account_id AND M2.IS_USE = 1
WHERE MP.IS_USE = 1