Drill 20: Beginner mistake — Transactions and locking

Name one mistake a beginner could make with this example.

Beginner 5 min read Lesson 325 of 480 Challenge included

What you will be able to do

Name one mistake a beginner could make with this example.

Practice task

Name one mistake a beginner could make with this example.

transfer.sqlSQL

CREATE TABLE accounts (
  id SERIAL PRIMARY KEY,
  balance NUMERIC(12, 2) NOT NULL DEFAULT 0
);

INSERT INTO accounts (balance) VALUES (1000.00), (500.00);

BEGIN;

UPDATE accounts SET balance = balance - 100 WHERE id = 1;
UPDATE accounts SET balance = balance + 100 WHERE id = 2;

COMMIT;

BEGIN;

UPDATE accounts SET balance = balance - 9999 WHERE id = 1;

ROLLBACK;

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Name one mistake a beginner could make with this example.

TEXT · starter

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Next: Drill 20: Real project — Debugging queries

Lesson 325 of 480 · 0% of course