Problem :
Table: Users
+————–+———+
| Column Name | Type |
+————–+———+
| account | int |
| name | varchar |
+————–+———+
account is the primary key for this table.
Each row of this table contains the account number of each user in the bank.
Table: Transactions
+—————+———+
| Column Name | Type |
+—————+———+
| trans_id | int |
| account | int |
| amount | int |
| transacted_on | date |
+—————+———+
trans_id is the primary key for this table.
Each row of this table contains all changes made to all accounts.
amount is positive if the user received money and negative if they transferred money.
All accounts start with a balance 0.
Write an SQL query to report the name and balance of users with a balance higher than 10000. The balance of an account is equal to the sum of the amounts of all transactions involving that account.
Return the result table in any order.
The query result format is in the following example.
Users table:
+————+————–+
| account | name |
+————+————–+
| 900001 | Alice |
| 900002 | Bob |
| 900003 | Charlie |
+————+————–+
Transactions table:
+————+————+————+—————+
| trans_id | account | amount | transacted_on |
+————+————+————+—————+
| 1 | 900001 | 7000 | 2020-08-01 |
| 2 | 900001 | 7000 | 2020-09-01 |
| 3 | 900001 | -3000 | 2020-09-02 |
| 4 | 900002 | 1000 | 2020-09-12 |
| 5 | 900003 | 6000 | 2020-08-07 |
| 6 | 900003 | 6000 | 2020-09-07 |
| 7 | 900003 | -4000 | 2020-09-11 |
+————+————+————+—————+
Result table:
+————+————+
| name | balance |
+————+————+
| Alice | 11000 |
+————+————+
Alice’s balance is (7000 + 7000 – 3000) = 11000.
Bob’s balance is 1000.
Charlie’s balance is (6000 + 6000 – 4000) = 8000.
———————————————————————————————————
SQL Schema:
Create table If Not Exists Users (account int, name varchar(20));
Create table If Not Exists Transactions (trans_id int, account int, amount int, transacted_on date);
Truncate table Users;
insert into Users (account, name) values (900001, ‘Alice’);
insert into Users (account, name) values (900002, ‘Bob’);
insert into Users (account, name) values (900003, ‘Charlie’);
Truncate table Transactions;
insert into Transactions (trans_id, account, amount, transacted_on) values (1, 900001, 7000, ‘2020-08-01’);
insert into Transactions (trans_id, account, amount, transacted_on) values (2, 900001, 7000, ‘2020-09-01’);
insert into Transactions (trans_id, account, amount, transacted_on) values (3, 900001, -3000, ‘2020-09-02’);
insert into Transactions (trans_id, account, amount, transacted_on) values (4, 900002, 1000, ‘2020-09-12’);
insert into Transactions (trans_id, account, amount, transacted_on) values (5, 900003, 6000, ‘2020-08-07’);
insert into Transactions (trans_id, account, amount, transacted_on) values (6, 900003, 6000, ‘2020-09-07’);
insert into Transactions (trans_id, account, amount, transacted_on) values (7, 900003, -4000, ‘2020-09-11’);
Solution :
SELECT
u.name, SUM(t.amount) AS balance
FROM
transactions t
LEFT JOIN
users u ON (t.account = u.account)
GROUP BY t.account , u.name
HAVING SUM(amount) > 10000;