TSQL

T-SQL, short for Transact-SQL, is Microsoft’s and historically Sybase’s proprietary extension to the SQL standard used for interacting with relational databases. It originated as an extension to Sybase ASE’s SQL and was adopted and expanded by Microsoft for its SQL Server product family. Today, T-SQL is the primary language for querying, managing, and programming SQL Server databases and is also used in Azure SQL Database and related cloud offerings.

T-SQL extends standard SQL with procedural programming features, including variables, conditional logic (IF...ELSE), loops (WHILE), and structured error handling (TRY...CATCH or THROW). It provides transaction control with BEGIN TRANSACTION, COMMIT, and ROLLBACK, enabling reliable, multi-statement operations. T-SQL supports the creation of reusable program units such as stored procedures, user-defined functions, triggers, and views, as well as extensive DDL and DML statements for data definition and manipulation. The language includes numerous built-in functions for string, numeric, date, and metadata operations, as well as system catalog views and metadata functions to query database structure.

While T-SQL remains closely tied to Microsoft’s ecosystem, some features are designed to be compatible with standard SQL, and certain functionality is not portable to other database systems. Developers typically write T-SQL code in environments such as SQL Server Management Studio or through programmatic access in applications, deploying it in SQL Server, Azure SQL Database, or related cloud services.