I listen a number of podcasts. Often I hear the expression "Order line" in the context of database or business object modelling. It seems to be the canonical example of something. I just don't know what.
So what is an "order line"? What concept does it represent in a canonical example?
It refers to a "Purchase Order" which typically consists of one or more lines, called "Order Lines".
As almost every business on earth has some similar record of its orders, purchases and/or sales, it has been the canonical real-world data example of a Parent-Child (or Master-Detail) relationship for as long as databases have existed (well over forty years).
It might look like this:
May Weller, 14-FEB-2011
qty Product Price
1 Hose, 50ft $21.99
4 Sprinkler $33.78
1 Gum $ 1.10
Total $56.87
This would typically be stored as one row in an [ORDERS] table and three additional rows in an [Order-Lines] table, that all point back to the parent row in [ORDERS]. Which could look something like this:
[ORDERS] Table:
OrderID: 14028
Customer: May Weller
OrderDate: 14-FEB-2011
[OrderLines] Table:
OrderLineID: 223011 223012 223013
OrderID: 14028 14028 14028
quantity: 1 4 1
Product: Hose, 50ft Sprinkler Gum
Price: 21.99 33.78 1.10
(NOTE: yes, I know that this is not fully normalized yet).