Many people wonder why relational databases are called “relational.” Some think that it’s because of a logical entity-relationship model you often start your design with. Or, because you have tables and relationships (aka foreign keys) between them. But that’s not the case. The name comes from the mathematical notion of “relation.” It all started with E. F. Codd who in 1970 (in the article A Relational Model of Data for Large Shared Data Banks) proposed something now called relational algebra as the mathematical foundation of databases.