- Understanding the Structure of a Relational Database
- What Is Involved in the Database Design Process?
- A Brief Introduction to Access
- Building Our Access Database
- Understanding the Limitations of an Access Database
- Expanding Your Database Vocabulary
What Is Involved in the Database Design Process?
After you are familiar with how a relational database works, you're ready to look specifically at the project at hand and determine what your database should look like and how it should behave. There are many ways to approach the development of a new database, but over the years, I have developed a six-step process that allows me to think through the database one step at a time. I have found that if I follow this process from beginning to end, I usually end up with a good database that functions as expected.
To see how well this process works, let's build a scenario and walk through the steps to see how they work. Suppose that you and I own a small consulting firm that specializes in developing database-driven Web applications for the business sector. Recently, we have been contacted by KrystalClear Technologies, a local startup company that is entering the telecommunications industry and offering residential and commercial telephone services. The company does not currently have a budget to hire an in-house database administrator and Web developer, so they have contacted our firm to explore the possibility of contracting for the development of a corporate intranet.
Although the decision makers at KrystalClear know that the functionality of the intranet must grow over time, they would like to start by having us develop four modules that would serve as the foundation for future developments. Those elements are the following:
A Human Resources employee management system. This system would allow the Human Resources staff to manage information about each employee hired by KrystalClear.
An Information Services asset management system. This element would allow the Information Technology staff to maintain information about the computer hardware, software, and peripherals owned by KrystalClear.
A departmental intranet management system. This system would allow a liaison in each department to update his individual departmental information page. This reduces the need to have staff from Information Services make updates to the intranet any time a department needs to make a change.
The front-end user interface for the intranet. This is the look and feel of the pages that the employees of KrystalClear will use on a daily basis. Although the management at KrystalClear has left this element up to your creative suggestions, they would like to be sure that the KrystalClear corporate logo is present on every page.
With that scenario in mind, let's proceed through the database design process and see what we can do.
The first step in designing a database is to consider the project you are working on and the features that your future users might want to have access to. I have found that during this step, it is extremely helpful to talk to both the management that is supervising the project and the end users who will work with the system on a daily basis to determine what they expect from the end-result and what issues they are trying to resolve.
Obviously, this is a hypothetical situation and we cannot sit down and talk with the managers and employees of KrystalClear. However, let's suppose we emailed a list of eight questions to an Intranet Coordinating Committee (a select group of employees and managers who have volunteered to work with us on the intranet project) and they have provided us with the following answers. In response to their answers, I have added some issues that we might need to consider (this is the thinking and talking part).
Q1: What reason or reasons do you have for developing this application?
A1: The purpose of developing our corporate intranet is to provide our employees with a single point of contact for information pertaining to our organization. Our intention is for any employee to be able to find directory information about other employees, learn about the internal activities of any department, and engage in activities such as requesting computer support, filling out employee benefit forms, or a variety of other activities that have previously been done via the telephone or in writing.
Thoughts about the answer: These all appear to be very good reasons for building an intranet. It appears that communication between users and departments is the highest priority.
Q2: Who are the anticipated users of the application?
A2: All employees located at our corporate offices should have access to the intranet via our local area network (LAN). Eventually, as we develop a wide area network (WAN), we would like employees at our outlying offices to be able to access the intranet as well.
Thoughts about the answer: Because the user of the intranet will currently be restricted to the LAN and not available to the outside world, external security is less of a concern than internal security. We should focus our efforts on ensuring that only the appropriate users have access to restricted areas of the system.
Q3: Are there any areas of the application that need to be secured? If so, how do you plan to designate which users are allowed to view those areas?
A3: Each departmental site will be secured in that editing it will only be allowed by the departmental manager and another departmental employee authorized by the manager. In addition, some departments, such as Human Resources, should have access to edit information that pertains to their jobs. This means that there will be sections of the Human Resources intranet site that only employees of HR will be able to access.
Thoughts about the answer: The Human Resources table that stores user details will need to have a field that specifies what department the user works for. From this, we can grant or deny access to restricted departmental information.
Q4: How many users do you anticipate accessing the system at the same time?
A4: At this time, all 125 employees should have access. We anticipate that 15 to 20 employees would be viewing information on the intranet at the same time.
Thoughts about the answer: Having 15 to 20 employees at a time viewing the data would probably result in at most 3 to 4 concurrent connections. This falls well within the restrictions on Microsoft Access, so we can use Access as our back-end database.
Q5: What is the projected growth for your company over the next five years with respect to employees?
A5: Over the next five years, we project having 400 to 500 employees; however, only 250 of those would be at the corporate office.
Thoughts about the answer: This projected growth would probably still be within the restrictions of an Access database, but we might want to recommend expansion to a SQL Server database should the company grow beyond these numbers.
Q6: If your company grows more quickly than anticipated, would be you open to upgrading the database?
A6: Yes. Unanticipated growth would most likely be caused by entrance into new markets, so we would be more than willing to fund software and hardware upgrades to meet our corporate needs.
Thoughts about the answer: An upsize to SQL Server would be relatively easy, however, the company should be notified of the hardware and licensing costs of SQL Server long before they reach the time to upsize.
Q7: You mentioned that you want each departmental manager and an additional liaison to be able to update their pages. What will be the procedure for indicating that an employee is allowed to make those changes?
A7: The departmental manager will email the Human Resources department the name of the employee selected to maintain their information. HR will then update the employee's record to indicate that she has permission.
Thoughts about the answer: The Human Resources table will need to have a field specifying whether the user is permitted to update the departmental site.
Q8: How will employees access the corporate intranet?
A8: Employees will access the intranet using their work computers. Our machines come configured with Microsoft Internet Explorer so users will use that browser to view the intranet.
Thoughts about the answer: Because all users will be on Internet Explorer, cross-browser compatibility is less of an issue than with a typical Web application. However, the company is anticipating a WAN in its future and it is not possible to project what browser remote offices might be using so we still need to code for all browsers.
As you can see, interacting with the Intranet Coordinating Committee has provided us with a wealth of information and has sparked questions of our own. After we feel our questions have been answered and we are satisfied with the amount of information that we have, it's time to move on to the next step.
Practice "Active Listening"
When talking with the people who will be using your new Web applications, it's a good idea to use a skill known as active listening where you not only listen to what they have to say, but respond to their statements with additional questions, comments, or observations. More often than not, your responses will generate more feedback on their part and provide you with additional information. Although this may sound like a no-brainer, you'd be surprised how often I have sat in on meetings where a technologist would sit quietly, listen, and take notes only to get back to his office and wonder about an issue that could have easily been asked and answered in the meeting.
The second step that I use in designing a database is to put myself in the place of the end user and try to anticipate any functionality that she might need that has not already been expressed. This process is often based on the conversations from the previous step and usually draws from my experience developing similar applications for other organizations.
For instance, with regard to the departmental updates of their own pages, the committee stated that the manager of the department would send an email to a member of the human resources staff indicating which employees should have permission to update the departmental site. From this, we can anticipate that the database table that stores the employee information should have a field that indicates whether the employee has access to update the page.
By anticipating these types of features, we can build our database in a manner that will better suit the application and we can forecast potential issues and address them with the committee.
Now that you have an understanding of what the organization is seeking and have used your past experiences to anticipate additional functionality, it's time to start building the application. We'll take a detailed look at the steps of building our intranet application for KrystalClear a little later in the chapter.
After the database has been developed, it is a very good idea to do some testing to ensure that it behaves as performed. Even though the KrystalClear employees won't directly interact with our intranet database through the use of Access, we can use Access to test some of the functionality that we know will be part of the application.
For instance, we know that our intranet application will be using queries based on the Structured Query Language (SQL) to add, edit, and modify data located in the database. Using the SQL View of Microsoft Access, shown in Figure 3.1, we can test those queries before we ever write a line of code for our Web pages.
Figure 3.1 The SQL View of Microsoft Access is just one tool that helps us test our application.
By running these tests, we can ensure that the data our database returns in response to the query is the information that we expected.
Unless you are really (and I mean really) good it's likely that the Analyze phase of the design process turned up some issues in your database that need to be resolved. Don't worry. No matter how long you build databases, you will probably always catch something that doesn't work correctly or needs some tweaking. During the Restructure phase, you can go back to make adjustments and resolve any issues that arise. After you make a change, however, it is important that you return to the Analyze phase and ensure that the changes you made did not cause problems with any other element of your database. After three or four iterations through the Analyze/Restructure phases, your database will be functioning properly and you'll be ready to move on to the last step.
Testing Your Changes
Be sure you test every change that is made during the Restructuring phase. Any modifications to the system require that you go back to Step 4 and restart until you are able to get through Step 5 with no changes.
Much like soldiers who are prepared for battle, at this point, your database should be ready to be deployed into action. This usually means the database structure and relationships have been thoroughly tested and everything functions as anticipated to begin the development of the Web pages that will interact with it.
Because we haven't begun developing our intranet database yet, let's take a few steps back to the Build phase and get cracking on our development.