Why Relationships Are Important

A relationship is an important component of a relational database.

  • It establishes a connection between a pair of tables that are logically related to each other. A pair of tables is logically related via the data each contains. For example, consider the tables in Figure 10.1

    Figure 10.1. A pair of logically related tables.

    image

    A logical relationship exists between the data in the STUDENTS table and the data in the STUDENT INSTRUMENTS table. A student can check out one or more instruments during the course of a school year, so a record in the STUDENTS table (representing the student) can be related to one or ...

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