In the beginning of the previous chapter, we discussed the importance of data in our everyday lives and gave examples of the kinds of data stored in databases. We then created our own data for the Companylink
database and discussed a little about its structure. However, sitting at rest within a database, that data is of little practical use. It is not enough to simply store data; it must be retrieved and manipulated to be useful. For instance, in order to use the data in the Companylink
database, we need to be able to perform practical operations such as the following:
Retrieve a list of the employees on Companylink, along with their street addresses, for a company mailing list
Retrieve employee names and their date of birth for a Happy Birthday application
Add and store new messages that employees send to one another
Change an employee's primary project when they are transferred to a new one
Remove the e-mail address of an employee when it is no longer valid
Add...