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Database Essentials
Introduction to Databases : Elements of a relational database : Tables


A table is a collection of logically related information treated as a unit. Tables are organized by rows and columns. The following figure shows the contents of a sample Customer table.
Figure 1. Columns and rows in the Customer table
Other common tables include an Order table in a retail database that tracks the orders each customer places, an Assignment table in a departmental database that tracks all the projects each employee works on, and a Student Schedule in a college database table that tracks all the courses each student takes.
Tables are generally grouped into three types:
*Kernel tables — Tables that are independent entities. Kernel tables often represent or model things that exist in the real world. Some example kernel tables are customers, vendors, employees, parts, goods, and equipment.
*Association tables — Tables that represent a relationship among entities. For example, an order represents an association between a customer and goods.
*Characteristic tables — Tables whose purpose is to qualify or describe some other entity. Characteristic only have meaning in relation to the entity they describe. For example, order-lines might describe orders; without an order, an order-line is useless.