This chapter introduces the student to the basic concepts of the course. The objectives important to this chapter are on page 1:
The chapter begins with a description of a company keeping business records in a spreadsheet. They are keeping all the information they seem to need about each sale, but the text points out that their methods are repetitive and wasteful, as well as potentially prone to error.
The simple flat file database that is their spreadsheet stores many information items redundantly. For instance, each order placed by a given customer features that customer's name and ID number. Needed information, of course, but it would take much less storage space to use a database instead. Each order presents the need to enter this same information, presenting the opportunity for error, which would cause data to be left out of reports that might be generated based on matching any one variation of the customer's name. A database allows us to store the customer's information in one place. This information is then accessed each time it is needed, providing for consistency.
The existing spreadsheet database is described more fully. Shortcomings of spreadsheets are described:
Before replacing the spreadsheet with a database management system, the company examines what information it wants to track.
Basic Database Terms
A common systems analysis technique is to determine what kind of reports you want from a system, as a aid to designing what must be stored in that system. An example of such a report that our company uses is a customer order. The sample order we are shown has three parts: a heading, a body, and a footing. Each part points out more data we must store, based on orders:
As noted above, examining this report tells us several more information items we need to store and track that were not described in the first three lists of information.
The text pauses here to introduce some common terms used in describing databases. This text defines a database as "a structure that contains information about many different categories of information and about the relationships between the categories". (Page 5) Not all databases are relational, but the most useful ones are. Another definition is on page 6, but we need to define some key terms first:
So, now we are ready for the definition on page 6: "a database is a structure that can store information about multiple types of entities, the attributes of those entities, and the relationships among the entities".
The text now examines the entities that our company is tracking, and tells us that we will create a table for each one. Each table describes on kind of entity (e.g. Sales Representatives). Rows in the table are instances of that entity (individual Sales Reps) and columns hold the attributes (e.g. LastName, FirstName, Commission). The first few tables are obvious: Rep, Customer, Orders, and Part should all be intuitive at this point. We are also shown a table called OrderLine, whose purpose is not obvious yet. It exists to satisfy a database design requirement that your book does not describe for another hundred thirty pages. The author's argument in this chapter is simply this: if we constructed a table of Orders, some orders would have more than one item in a given cell. This would cause problems later, in determining which items the customer ordered how many of. This is not allowed in standard databases. So, a rule is implied:
It is possible to read the various tables to answer the questions posed at this point in the chapter. Students should do so, for practice.
Description of Database Management Systems
Next, the text introduces the idea of a database management system (DBMS). This is any software solution that allows users to store and retrieve data, and produces reports needed by the users. Users interact with the DBMS directly or through an interface of some sort. Users typically can add, delete, and modify records through a DBMS. They should also be able to ask the DBMS to retrieve all orders for a specific part, or all commission payments to specific sales people. Making such a request is called running a query. (Query is another word for a question.)
Some examples of DBMSs are listed: Access, Oracle, DB2, and SQL Server. In the example in the text, the DBA, or Database Administrator (person who manages the database) designs the tables to be used and creates several forms that will be used in the user interface to the DBMS. Using a form, the users can add a new part to the Part table without knowing anything about database design themselves.
By creating a series of forms the DBA will create a switchboard system for the users. A switchboard system is a set of forms that users call up from a menu, each form allowing the users to perform a common function with the database.
Advantages and Disadvantages of Database Processing
'The text presents a standard list of virtues of database systems:
A short list of disadvantages to using a DBMS:
Introduction to the case study for the assignments
The assignments for this chapter are about a bookstore whose owner has created several tables of information: Branch, Publisher, Author, Book, Wrote, and Inventory. To practice reading tables and relating data, we will do several exercises in class based on these tables, and those in the body of the chapter.