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📘 Day 99: Transactions

Welcome to Day 99! Today, we'll learn about Transactions, a sequence of operations performed as a single logical unit of work.

What is a Transaction?

A transaction is a unit of work that is performed against a database. Transactions are used to ensure data integrity. All the statements in a transaction are executed as a single unit. If any statement in the transaction fails, the entire transaction is rolled back, and the database is left in its original state.

ACID Properties

Transactions have four standard properties, often referred to by the acronym ACID:

  • Atomicity: Ensures that all operations within a work unit are completed successfully. Otherwise, the transaction is aborted at the point of failure, and all the previous operations are rolled back to their former state.
  • Consistency: Ensures that the database properly changes states upon a successfully committed transaction.
  • Isolation: Enables transactions to operate independently of and transparent to each other.
  • Durability: Ensures that the result or effect of a committed transaction persists in case of a system failure.

Transaction Control Language (TCL)

BEGIN TRANSACTION

Starts a new transaction.

COMMIT

Saves all the changes made in the current transaction.

ROLLBACK

Undoes all the changes made in the current transaction.

SAVEPOINT

Creates a point within a transaction to which you can later roll back.

💻 Exercises: Day 99

Please see the exercises.sql file for today's exercises.

Previous: Day 98 – Day 98: Indexes • Next: Day 100 – Day 100: Stored Procedures

You are on lesson 99 of 108.