Transactions

Study the pattern

Transactions let you apply changes and commit or roll them back. Predict the output before running the example.

BEGIN; UPDATE orders SET amount=amount+100 WHERE order_id=101; SELECT order_id,amount FROM orders WHERE order_id=101; ROLLBACK;

Explain it from memory

What does today's SQL feature do, and when would you use it?

Run the statements together; ROLLBACK undoes the update.

Run SQL in your browser

Run the example, then modify one clause and predict how the result changes.

Run the statements together; ROLLBACK undoes the update.

Consolidate the skill

• Run and inspect the output.
• Change one part and predict the difference.
• Return later and rewrite the query from memory.