A Relational Model of Data for Large Shared Data Banks

Codd's 1970 paper proposed that data storage should be separated from its physical representation on disk and instead organized into relations — tables with rows and columns governed by mathematical set theory. At the time, programmers navigated databases by following pointers through hierarchical or network structures, coupling every application to the internal layout of the data. Codd's relational model eliminated that dependency in twelve pages, replacing navigational access with declarative queries that described what you wanted rather than how to get it. The paper was initially dismissed by IBM's own IMS team, whose hierarchical database was a commercial success, but by the early 1980s relational systems had won. Every SQL query written today descends directly from the algebra Codd formalized here. It remains one of the clearest examples in computing history of a single theoretical insight reorganizing an entire industry.