Databases Intermediate

What is Transaction?

A sequence of database operations that are treated as a single unit — either all succeed or all are rolled back.

Transactions ensure data consistency through ACID properties: Atomicity (all or nothing), Consistency (valid state transitions), Isolation (concurrent transactions don't interfere), and Durability (committed data persists).

Commands include BEGIN/START TRANSACTION, COMMIT (save changes), and ROLLBACK (undo changes). Isolation levels (READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE) balance consistency and performance.

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Related Terms

Row-Level Security (RLS)

A database feature that restricts which rows a user can access in a table based on security policies.

CTE (Common Table Expression)

A temporary named result set defined within a SQL statement using the WITH clause, improving query readability and enabling recursion.

A query that transforms rows into columns, creating a pivot table view of aggregated data.

Write-Ahead Log (WAL)

A technique where changes are first written to a log before being applied to the database, ensuring crash recovery and data integrity.

Database Sharding

A horizontal scaling strategy that distributes data across multiple database servers based on a partition key.

ETL (Extract, Transform, Load)

A data pipeline process that extracts data from sources, transforms it into a suitable format, and loads it into a destination system.

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