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CREATE TABLE accounts (
account_id SERIAL PRIMARY KEY,
account_holder VARCHAR(100),
account_type VARCHAR(50)
);
CREATE TABLE transactions (
transaction_id SERIAL PRIMARY KEY,
account_id INTEGER REFERENCES accounts(account_id),
amount DECIMAL(12,2),
transaction_type VARCHAR(20),
transaction_date DATE
);
INSERT INTO accounts (account_holder, account_type) VALUES
('Alice Johnson', 'Savings'),
('Bob Smith', 'Checking');
INSERT INTO transactions (
account_id,
amount,
transaction_type,
transaction_date
) VALUES
(1, 1500, 'deposit', '2025-01-01'),
(1, 300, 'withdrawal', '2025-01-10'),
(2, 2200, 'deposit', '2025-01-03'),
(2, 500, 'withdrawal', '2025-01-15');
SELECT
account_id,
SUM(
CASE
WHEN transaction_type = 'deposit' THEN amount
ELSE -amount
END
) AS current_balance
FROM transactions
GROUP BY account_id;
SELECT
transaction_date,
amount,
SUM(amount) OVER (
ORDER BY transaction_date
) AS running_total
FROM transactions;Coding works best on desktop or with an external keyboard.
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