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In Depth Information
3 Maintaining a Database
Introduction
Once a database has been created and loaded with data, it must be maintained. Maintaining
the database means modifying the data to keep it up-to-date, such as adding new records,
changing the data for existing records, and deleting records. Updating can include mass
updates or mass deletions; that is, updates to, or deletions of, many records at the same time.
Maintenance of a database can also involve the need to restructure the database
periodically; that is, to change the database structure. Restructuring can include adding
new fi elds — including both Lookup and multivalued fi elds — to a table, changing the
characteristics of existing fi elds, and removing existing fi elds. It also includes the creation of
validation rules and referential integrity. Validation rules ensure validity of the data in the
database, while referential integrity ensures the validity of the relationships.
Maintaining a database also can include fi ltering records, a process that ensures that
only the records that satisfy some criterion appear when viewing and updating the data in
a table. Changing the appearance of a datasheet is a maintenance activity. Finally, backing
up the database as well as compacting and repairing a database are database maintenance
tasks as well.
Project — Maintaining a Database
JSP Recruiters faces the task of keeping its database up-to-date. As the agency takes on new
clients and recruiters, it will need to add new records, make changes to existing records, and
delete records. JSP managers have found they must change the structure of the database to
categorize the clients by type. They will do this by adding a Client Type fi eld to the Client
table. They also want to track the specialties that are of interest to clients. They will do so
by adding a Specialties Needed fi eld to the Client table. Because clients may need more than
one specialty, this fi eld will be a multivalued fi eld. Along with these changes, JSP staff want
to change the appearance of a datasheet when displaying data.
JSP would like the ability to make mass updates, that is, to update or delete
many records in a single operation. They want rules that make sure users can enter
only valid data into the database, and they want to ensure that it is not possible for the
database to contain a client who is not associated with a specifi c recruiter. Finally, they
want to improve the effi ciency of certain types of processing, specifi cally sorting and
retrieving data.
AC 138
AC 138
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