Databases Reference
In-Depth Information
Figure 5.1
Schema snippet from an operational database.
general comments, such as notes on phone conversations with the customer regarding
the invoice.
An invoice may list a variety of items, each on its own line. For example, you may
have purchased blue widgets, which shipped on October 23, 2006, the quantity being
100 at a unit price of $2.50 each, for a sell value of $250. You may also have purchased
red widgets, which appear on another line on the same invoice. This data is stored in the
Line_Item table.
Each line item is associated with a job that was manufactured by the plant. The Job
table contains the specifications for the job. The details of the Job table are not shown
here, since those details do not enter into our discussion.
The Job_Costing table contains data tracking the time and costs expended in pro-
ducing each job. When a job reaches a machine, the employee at that machine scans a
job ID on the job ticket. The employee also scans a cost center bar code representing the
operation to be performed, and a bar code containing their employee ID. The start and
stop times for the operation are automatically recorded by the computer system. The
data is stored in the Job_Costing table, along with the hourly rate for the cost center,
