SQLCLR allows integration of .NET Framework CLR components in SQL SERVER. .NET CLR Assemblies reside and run from database rather than file system. SQL SERVER need to check only once during deployment. This boosts performance and reliability.
SQLCLR allows to write stored procedures, functions, triggers, user defined types and aggregates using variety of .NET Framework languages like C#, VB.NET etc.
When to use SQLCLR?
Don't use SQLCLR for querying data from SQL SERVER. It is better to use T-SQL for that. Instead use SQLCLR when you can't perform some tasks using native SQL functions like GZip Compression/Decompression, PGP Encryption/Decryption, complex string manipulations etc.
How to enable SQLCLR?
exec sp_configure 'clr enabled', 1; GO RECONFIGURE GO