Microsoft SQL Server (MSSQL) is a relational database management system developed by Microsoft.
Microsoft SQL Server (Structured Query Language) is a proprietary relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications—which may run either on the same computer or on another computer across a network (including the Internet). Microsoft markets at least a dozen different editions of Microsoft SQL Server, aimed at different audiences and for workloads ranging from small single-machine applications to large Internet-facing applications with many concurrent users.
Microsoft's SQL Server is a suite of relational database management system (RDBMS) products providing multi-user database access functionality. It originated from the Sybase SQL Server 4.x codebase and Transact-SQL dialect (t-sql), but it has forked significantly since then.