The relational database model was conceived by E. F. Codd in 1969, then a researcher at IBM. The model is based on branches of mathematics called
- set theory and
- predicate logic.
The basic idea behind the relational model
is that a database consists of a series of unordered tables (or relations) that can be manipulated using non-procedural operations that return tables. This model was in vast contrast to the more traditional database theories of the time that were much more complicated, less flexible and dependent on the physical storage methods of the data.
It is commonly thought that the word relational in the relational model comes from the fact that you relate together tables in a relational database. Although this is a convenient way to think of the term, it is not accurate. Instead, the word relational
has its roots in the terminology that Codd used to define the relational model
. The table in Codd's writings was actually referred to as a relation (a related set of information). In fact, Codd uses the terms relations, attributes and tuples where most of us use the more common terms tables, columns and rows, respectively (or the more physical and thus less preferable for discussions of database design theory files, fields and records). The relational model can be applied to both databases and database management systems (DBMS) themselves.
The relational trustworthiness of database programs can be analyzed using Codd's 12 rules. Since Codd's paper on the relational model, the number of rules has been expanded to 300 for determining how DBMS products conform to the relational model. When compared with other database management programs, Microsoft Access fares quite well in terms of relational trustworthiness
. Still, it has a long way to go before it meets all twelve rules completely