T-SQL - Transact-SQL: T-SQL

T-SQL or Transact SQL is Microsoft implementation of Structured Query Language. It is used with Microsoft SQL Server. Transact-SQL, an extension to the SQL database programming language, is a powerful language offering many features - a wide variety of datatypes, temporary objects, system and extended stored procedures, scrollable cursors, conditional processing, transaction control, exception and error handling, and much more.

SQL and the Introduction of Transact-SQL

SQL, on which Transact-SQL is based, started life in the mid-1970s as an IBM product called SEQUEL. SEQUEL stood for Structured English Query Language. After a permutation or two and some legal problems, IBM changed the name to SQL - the Structured Query Language. The language was designed to provide a standard method for accessing data in a relational database. Ironically, although IBM introduced SQL, Oracle was the first to bring a SQL-using product to market.

Today, many different relational database systems utilize SQL as the primary means for accessing and manipulating data. When the American National Standards Institute (ANSI) published a standard for the SQL language in 1989, they set a universal standard to which database vendors could adhere. Later, in 1992, ANSI released an update to the SQL standard, known as SQL-92. The standards helped formalize many of the behaviors and syntax structures of SQL. The ANSI standard covered lots of important details concerning the querying and manipulation of data. The syntax was formalized for many commands; some of these are SELECT, INSERT, UPDATE, DELETE, CREATE, and DROP.

Unfortunately, the standards didn't address every facet of programming for a relational database. To meet the needs of their own user communities, database vendors began to extend the SQL language with capabilities that enhanced the basic functionality of SQL. The Transact-SQL language was introduced by Sybase to answer user requirements for programming extensions to SQL - extensions enabling conditional processing, error handling, declared variables, row processing, and numerous other functions. Even some of the simplest operations, like creating an index or performing a conditional operation, are extensions to the SQL language.

Furthermore, many relational database products had been on the market for some time before a standard of any kind had been published. As a result, many developers began to implement their own extensions to the SQL language. In most cases, these extensions to SQL were incompatible from vendor to vendor. A program written in Oracle's dialect of SQL, for example, wouldn't run properly under Sybase or DB2 and vice versa unless it contained only the simplest ANSI-standard SQL statements.