Databases penetrate virtually every branch of human activity, with relational databases (RDBMS) becoming the de-facto standard. Some legacy database models — hierarchical and network databases — are still in use, but relational database model (RDBM) holds the lion's share of the market.
The RDBM resolves some of the inherent problems of the legacy databases, and — with the advent of faster hardware and support from the industry heavyweights — became the staple of every business enterprise. The new object-oriented databases (OODMS) and object-oriented relational database systems (OORDBMS) are evolving, though none has reached the level of acceptance comparable with that of RDBMS.
Most of the existing applications on the market database use SQL as the standard language. There are three (four, by some counts, if SQL86 is included) standards: SQL89, SQL92, and SQL99, with virtually every RDBMS product being at least partially SQL92 compliant.