Transactions in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a transaction in the context of NestJS and databases?

A transaction is a sequence of database operations that are treated as a single unit. Either all operations succeed (commit) or all fail (rollback), ensuring data consistency.

intermediate

How do you start a transaction using TypeORM in NestJS?

You use the QueryRunner from TypeORM to start a transaction by calling queryRunner.startTransaction().

beginner

What happens if an error occurs inside a transaction block in NestJS?

If an error occurs, the transaction is rolled back, undoing all changes made during the transaction to keep data consistent.

beginner

Why should you use transactions when updating multiple related database records?

Transactions ensure that all related updates succeed together or fail together, preventing partial updates that could cause data errors.

intermediate

What is the role of EntityManager in NestJS transactions?

EntityManager allows you to perform database operations within a transaction context, managing queries and commits or rollbacks.

Which method starts a transaction using TypeORM's QueryRunner in NestJS?

A initTransaction()

B startTransaction()

C openTransaction()

D begin()

The correct method to start a transaction is startTransaction().

What happens if you forget to commit a transaction in NestJS?

A Changes are lost after the transaction ends

B Changes are saved automatically

C An error is thrown immediately

D The transaction rolls back automatically

If you don't commit, changes made inside the transaction are lost when it ends.

Which NestJS component helps manage database operations inside a transaction?

A EntityManager

B Controller

C Service

D Module

EntityManager manages database operations within transactions.

Why use transactions when updating multiple tables?

A To speed up queries

B To avoid using indexes

C To ensure all updates succeed or fail together

D To reduce server load

Transactions ensure all related updates succeed or fail as one unit.

Which of these is NOT a transaction step in NestJS with TypeORM?

A startTransaction()

B commitTransaction()

C rollbackTransaction()

D executeTransaction()

executeTransaction() is not a standard TypeORM transaction method.

Explain how transactions help maintain data integrity in NestJS applications.

Think about what happens if one update fails among many.

Describe the steps to implement a transaction using TypeORM's QueryRunner in NestJS.

Follow the lifecycle of a transaction from start to finish.