What is T-SQL?

T-SQL, short for Transact-SQL, is not one thing but a set of programming extensions for Sybase and Microsoft.

The programming extensions basically act as as extension to Structured Query Language, SQL is designed to allow users to interact with relational databases.

T-SQL is regarded as an extension of SQL since it comes with additional features such as; procedural programming, local variables/error handling and data processing.

What is essential for T-SQL?