
Microsoft SQL Server is a relational database management system (RDBMS) produced by Microsoft. Its primary query language is Transact-SQL, an implementation of the ANSI/ISO standard Structured Query Language (SQL) used by both Microsoft and Sybase.
The architecture of Microsoft SQL Server is broadly divided into three components: SQLOS which implements the basic services required by SQL Server, including thread scheduling, memory management and I/O management; the Relational Engine, which implements the relational database components including support for databases, tables, queries and stored procedures as well as implementing the type system; and the Protocol Layer which exposes the SQL Server functionality.