Basics of Querying
Understanding the Foundations Standard SQL is based on the relational model, which is a mathematical model for data management and manipulation. The relational model was initially created and proposed by Edgar F. Codd in 1969. Since then, it has been explained and developed by Chris Date, Hugh Darwen, and others. the true source for the model’s name is the mathematical concept relation. A relation in the relational model is what SQL calls a table. The two are not synonymous. SQL attempts to represent with a table: a relation has a heading and a body. The heading is a set of attributes (what SQL attempts to represent with columns), each of a given type. An attribute is identified by name and type name. The body is a set of tuples (what SQL attempts to represent with rows). Each tuple’s heading is the heading of the relation. Each value of each tuple’s attribute is of its respective type. Some of the most important principals to understand about SQL stem from the relational
