Relational Model Concepts

The relational model represents the database as a collection of relations. Informally, each relation resembles a table of values or, to some extent, a "flat" file of records. For example, the database of files that was shown in Figure 01.02 is considered to be in the relational model. However, there are important differences between relations and files, as we shall soon see.
When a relation is thought of as a table of values, each row in the table represents a collection of related data values. We introduced entity types and relationship types as concepts for modeling real-world data in Chapter 3. In the relational model, each row in the table represents a fact that typically corresponds to a real-world entity or relationship. The table name and column names are used to help in interpreting the meaning of the values in each row. For example, the first table of Figure 01.02 is called STUDENT because each row represents facts about a particular student entity. The column names—Name, StudentNumber, Class, Major—specify how to interpret the data values in each row, based on the column each value is in. All values in a column are of the same data type.