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2026-07-29 16:01
Database

Basic Transaction

QueryValidateHard
Try Interactive Demo

What you will learn

  • Wrap mutations in BEGIN / COMMIT; on exception ROLLBACK — test both happy and failure paths with a seeded failure
  • Isolation levels (READ COMMITTED / REPEATABLE READ / SERIALIZABLE) produce different results under races — pin explicitly
  • SAVEPOINT allows partial rollback within a transaction — useful when batch ops partially succeed and partially fail

Description

Transfer stock between products atomically.

Test Scenario

-- Transfer 10 units from product 1 to product 2
BEGIN TRANSACTION;

UPDATE products SET stock = stock - 10 WHERE id = 1;
UPDATE products SET stock = stock + 10 WHERE id = 2;

-- Verify before commit
SELECT id, name, stock FROM products WHERE id IN (1, 2);

COMMIT;

-- If error occurred, use ROLLBACK instead

Testing Tips

  • •BEGIN starts a transaction
  • •COMMIT saves changes
  • •ROLLBACK undoes changes
  • •All or nothing execution
// Playwright API Testing - Database
import { test, expect } from '@playwright/test';


test('Database query via API', async ({ request }) => {
  const response = await request.post('/api/database/query', {
    data: {
      sql: 'SELECT * FROM users WHERE id = ?',
      params: [1]
    }
  });


  expect(response.ok()).toBeTruthy();
  const { rows } = await response.json();
  expect(rows.length).toBeGreaterThan(0);
});

Challenge ID: sql-transaction-basic

2 frameworks available