Transact SQL

Transact-SQL (T-SQL) is an extension to SQL developed by Microsoft and Sybase. Transact-SQL is the programming language for the commands used to administer SQL Server, create and manage objects in a physical or virtual instance of SQL Server, as well as to insert, retrieve, modify and delete data in SQL Server tables.  The SQL standards published by the International Standards Organization (ISO) and the American National Standards Institute (ANSI) defined a software language, and Transact-SQL was developed and extended from this definition.

T-SQL extends the SQL standard to include procedural programming, local variables, support functions for string processing, data processing, math and so forth, as well as modifications to DELETE and UPDATE statements.

Furthermore, applications can only communicate with SQL Server by sending Transact-SQL statements to the server.

According to Microsoft SQL Server TechNet, the following applications use T-SQL to communicate with SQL Server:

1. General office applications;

2. Applications using a graphical user interface to select the tables and columns to view data from;

3. Applications that use general language sentences to define the data a user wants to view;

4. Business applications that store data in SQL Server databases;

5. Transact-SQL scripts that are run by utilities like sqlcmd;

6. Applications created with development systems including Microsoft Visual C++, Microsoft Visual Basic, or Microsoft Visual J++ that use database APIs such as ADO, OLE DB, and ODBC;

7. Web pages that extract data from SQL Server databases;

8. Distributed database systems where SQL Server is replicated to various databases or distributed queries are executed;

9. Data warehouses in which data is taken from online transaction processing systems and synopsized for decision-support analysis.