A database that maintains a set of separate, related files (tables), but combines data elements from the files for queries and reports when required. The concept was developed in 1970 by Edgar Codd, ...

A question asked about data contained in two or more tables in a relational database. The relational query must specify the tables required and what the condition is that links them; for example, ...

Relational database management systems (RDBMS) rely on an optimizer (or relational optimizer) that transforms SQL statements into executable code. Before any SQL statement can be run by the RDBMS, the ...