Database Reference
In-Depth Information
When the subject of a table is an event, it means that the table represents something that
occurs at a given point in time having characteristics you wish to record. You can store
these characteristics as data and then process the data as information in exactly the same
manner as a table that represents some specific object. Examples of events you may need
to record include judicial hearings, distributions of funds, lab test results, and geological
surveys.
Figure 3.7
shows an example of a table representing an event that we all have ex-
perienced at one time or another—a doctor's appointment.
Figure 3.7. A table representing an event
A table that stores data used to supply information is called a
data table,
and it is the most
commontypeoftableinarelationaldatabase.Datainthistypeoftableisdynamicbecause
youcanmanipulate it(modify,delete, andsoforth)andprocessitintoinformation insome
formorfashion.You'llconstantly interact withthesetypesoftablesasyouworkwithyour
database.
A
validation table
(also known as a
lookup table
), on the other hand, stores data that you
specifically use to implement data integrity. A validation table usually represents subjects,
suchascitynames,skillcategories,productcodes,andprojectidentificationnumbers.Data
in this type of table is static because it will very rarely change at all. Although you have
very little
direct
interaction with these tables, you'll frequently use them
indirectly
to val-
idate values that you enter into a data table.
Figure 3.8
shows an example of a validation
table.
