T-SQL (Transact-SQL) is a set of programming extensions from Sybase and Microsoft that add several features to the Structured Query Language (SQL), including transaction control, exception and error handling, row processing and declared variables.

All applications that communicate with SQL Server do so by sending T-SQL statements to the server. T-SQL queries include the SELECT statement, selecting columns, labeling output columns, restricting rows and modifying a search condition.

T-SQL identifiers, meanwhile, are used in all databases, servers, and database objects in SQL Server. These include tables, constraints, stored procedures, views, columns and data types. T-SQL identifiers must each have a unique name, are assigned when an object is created and are used to identify an object.