Difference between Read Committed and Read Uncommitted Isolation Level in SQL Server

Difference between Read Committed and Read Uncommitted Isolation Levels in SQL Server.

Isolation levels determine the behavior of concurrent users that read or write data.

A Reader is one who is selecting some records using a shared lock by default whereas writer mean the one who is making modification in the tables and required an exclusive lock.
We can control the way reader behave by setting different Isolation levels.

You can set type six types of isolation levels: READ UNCOMMITTED, READ COMMITTED (default), REPEATABLE READ,  SERIALIZABLE, SNAPSHOT, and READ COMMITTED SNAPSHOT.

The Default Isolation Level is Read committed.You can override the default isolation level.

Below is the Explanation and difference between Read committed and Read Uncommitted Isolation levels.

A reader that doesn't ask for a shared lock can never be in conflict with a writer that is holding an exclusive lock.This means that that reader can read uncommitted changes (also known as dirty reads).

It also means that the reader won’t interfere with a writer that asks for an exclusive lock. In other words, a writer can change data while a reader that is running under the READ UNCOMMITTED isolation level reads data.