Dynamics NAV 2013 stores its data in a Microsoft SQL database. Previous versions of Dynamics NAV could either use a Microsoft SQL database or a native database for Dynamics NAV. The native database has been discontinued and is no longer available.
The database used by Dynamics NAV is a relational database, but it does not fully implement the referential integrity concept that ensures that relationships between tables remain consistent. In Dynamics NAV, data integrity is maintained partially by the database engine itself and mainly by code. Sometimes, it is not even maintained.
When developing new Dynamics NAV functionalities, consider data integrity inside your analysis and design work.