Calculate balances in transactions table where users send money to each other

user_9373781 0
Viewed 365

I have a transaction table set up like this: 

-- Transactions table
+----+---------+-------+------------------+--------+-----------+
| id | from_id | to_id | transaction_type | amount | card_type |
+----+---------+-------+------------------+--------+-----------+
| 1  | 1       | 1     | deposit          | 90     | debit     |
| 2  | 1       | 2     | transfer         | -60    | debit     |
| 3  | 2       | 2     | deposit          | 10     | debit     |
| 4  | 2       | 2     | deposit          | 20     | credit    |
+----+---------+-------+------------------+--------+-----------+

If i deposit it should show a positive value to show that money was added to my account, but if i do a transfer it should use a negative balance to show that money was removed from my account. The issue is, I can't think of a query that would add the money to the user 2 account from the transfer of user 1 to produce a view like this (based on card type): 

-- Debit Balance Table
+---------+---------+
| user_id | balance |
+---------+---------+
| 1       | 30      |
| 2       | 70      |
+---------+---------+

-- Credit Balance Table
+---------+---------+
| user_id | balance |
+---------+---------+
| 1       | 0       |
| 2       | 20      |
+---------+---------+

I know you can't add money to a credit account but just forget that logic for now.

mysql sql
1 Answers

For debit, you can simply do conditional aggregation:

SELECT 
  all_users.user_id, 
  SUM (CASE 
         WHEN t.transaction_type = 'deposit' AND all_users.user_id = t.from_id
           THEN ABS(t.amount) 
         WHEN t.transaction_type = 'transfer' AND all_users.user_id = t.from_id
           THEN -ABS(t.amount)
         WHEN t.transaction_type = 'transfer' AND all_users.user_id = t.to_id
           THEN ABS(t.amount)
         ELSE 0
       END
      ) AS balance 
FROM transactions AS t 
JOIN (
      SELECT from_id AS user_id FROM transactions 
      UNION 
      SELECT to_id FROM transactions
     ) AS all_users 
  ON t.from_id = all_users.user_id OR 
     t.to_id = all_users.user_id 
WHERE t.card_type = 'debit' 
GROUP BY all_users.user_id
user_24693080
Related