This graphic shows an example ER diagram for a purchase order application.

The elements of the diagram are as follows:

• A rectangle representing the Purchase Order entity type
• A rectangle representing the Customer entity type
• A rectangle representing the Line Item entity type
• A rectangle representing the Stock Item entity type
• Each of the entity types is modified by several ovals representing attributes. The attributes of each entity types are listed later in this description.
• Relationships are represented between the entity types. The relationships are discussed in the following list and in the text following the figure.

End of elements list.

The relationships between the entity types are listed here and discussed further in the text following the figure.

• A Customer places one or more Purchase Orders.
• One or more Purchase Order refers to one or more Stock Items.
• A Purchase Order lists one or more Line Items.
• One or more Line Items refer to one Stock Item.

End of relationship list.

The following attributes modify the entity types:

• The Customer entity type has the following attributes:
  customer_number, customer_name, street, city, state, zip_code, and phone_number.
• The Purchase Order entity type has the following attributes:
  p_o_number, customer_number, order_date, ship_date, to_street, to_city, to_state, and to_zip_code.
• The Line Item entity type has the following attributes:
  line_item_number, p_o_number, stock_item_number, quantity, and discount.
• The Stock Item entity type has the following attributes:
  stock_item_number, description, and price.

End of attribute list.

End of description.