Final_Account_Balance.SQL

--Final Account Balance

Given a table of bank deposits and withdrawals, return the final balance for each account.

Assumption:

All the transactions performed for each account are present in the table; no transactions are missing.
transactions Table:
Column Name	Type
transaction_id	integer
account_id	integer
transaction_type	varchar
amount	decimal
transactions Example Input:
transaction_id	account_id	transaction_type	amount
123	101	Deposit	10.00
124	101	Deposit	20.00
125	101	Withdrawal	5.00
126	201	Deposit	20.00
128	201	Withdrawal	10.00
Example Output:
account_id	final_balance
101	25.00
201	10.00
Explanation:
In total, $30.00 were deposited to account 101, and $5.00 were withdrawn. Therefore, the final balance will be $30.00-$5.00 = $25.00

-- Solution
SELECT ACCOUNT_ID, 
SUM(
CASE 
  WHEN TRANSACTION_TYPE = 'Deposit' THEN AMOUNT
  ELSE -AMOUNT
END 
) AS FINAL_BALANCE
FROM transactions
group by ACCOUNT_ID