Getting Started with InfoSphere Data Architect

Chapter 3 – Logical Data Modeling 59
Note:
If you don’t know what data type to choose, keep in mind the following considerations:
• If an attribute or column is designed for arithmetic calculations, use a numeric data
type.
• Use text data types for all other attributes for the following reasons:
- Text data types are more flexible; for example, you can use constraints to reduce
storage size of data.
- You can better control the input of text data types because DB2 offers more
functions for string data types.
However, sometimes you should use a numeric data type if you want the primary key to also
be numeric (for example, surrogate keys are also numeric).
Note that when you add attributes to the entity, the diagram is also updated. The
STUDENT ID entity is now displayed in the key compartment of the STUDENT entity in the
diagram, with an icon next to it to indicate that STUDENT ID is the primary key of the
entity.
Follow the same process outlined above to add more other attributes to the STUDENT
entity. Add the following attributes to the STUDENT entity:
4. Add the FIRST NAME attribute. The attribute has a data type of VARCHAR(20)
and is required.
5. Add the LAST NAME attribute. The attribute has a data type of VARCHAR(50) and
is required.
6. Add the START DATE attribute. The attribute has a data type of DATE.
7. Add the GRADUATION DATE attribute. The attribute has a data type of DATE.
8. Save your work.
You have used the diagram editor to create a complete entity, as seen in Figure 3.8. Now
let's learn how to use the Data Project Explorer to create another entity.