Transaction handling in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a transaction using a Node.js database client.

Node.js

const client = await pool.connect();
try {
  await client.query('[1]');
  // perform queries
} finally {
  client.release();
}

Drag options to blanks, or click blank then click option'

AbeginTransaction

BBEGIN

CstartTransaction

DinitTransaction

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'beginTransaction' which is not the correct command name in this client.

Using 'startTransaction' or 'initTransaction' which do not exist.

In Node.js database clients like 'pg', the SQL command to start a transaction is BEGIN.

2fill in blank

medium

Complete the code to commit the transaction after successful queries.

Node.js

try {
  await client.query('INSERT INTO users(name) VALUES($1)', ['Alice']);
  await client.query('[1]');
} catch (e) {
  await client.query('ROLLBACK');
}

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ACOMMIT

Bfinalize

Csave

DcommitTransaction

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'commitTransaction' which is not a command in this context.

Using 'save' or 'finalize' which are not valid transaction commands.

The SQL command to save changes in a transaction is COMMIT.

3fill in blank

hard

Fix the error in the code to rollback the transaction on error.

Node.js

try {
  await client.query('UPDATE accounts SET balance = balance - 100 WHERE id = $1', [accountId]);
  await client.query('UPDATE accounts SET balance = balance + 100 WHERE id = $2', [recipientId]);
  await client.query('COMMIT');
} catch (e) {
  await client.query('[1]');
}

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Acancel

BrollbackTransaction

CROLLBACK

Dundo

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'rollbackTransaction' which is not a command in this client.

Using 'cancel' or 'undo' which are not valid transaction commands.

The correct SQL command to undo changes in a transaction is ROLLBACK.

4fill in blank

hard

Fill both blanks to correctly handle transaction with async/await.

Node.js

async function transferFunds(client, fromId, toId, amount) {
  try {
    await client.query('[1]');
    await client.query('UPDATE accounts SET balance = balance - $1 WHERE id = $2', [amount, fromId]);
    await client.query('UPDATE accounts SET balance = balance + $1 WHERE id = $2', [amount, toId]);
    await client.query('[2]');
  } catch (error) {
    await client.query('ROLLBACK');
    throw error;
  }
}

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ABEGIN

BCOMMIT

Cstart

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' or 'end' which are not valid transaction commands.

Not committing after beginning the transaction.

Transactions start with BEGIN and end with COMMIT to save changes.

5fill in blank

hard

Fill all three blanks to create a transaction that rolls back on error and releases the client.

Node.js

const client = await pool.connect();
try {
  await client.query('[1]');
  await client.query('DELETE FROM orders WHERE id = $1', [orderId]);
  await client.query('[2]');
} catch (err) {
  await client.query('[3]');
  throw err;
} finally {
  client.release();
}

Drag options to blanks, or click blank then click option'

ABEGIN

BCOMMIT

CROLLBACK

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' instead of 'BEGIN' to start the transaction.

Not rolling back on error.

Not committing after successful queries.

Start the transaction with BEGIN, save changes with COMMIT, and undo changes with ROLLBACK on error.