Test your knowledge before advancing

Before you move on to the next chapter, let's quickly review what you've learned so far about attributes and key constraints. If you're unsure about the answer, please quickly review chapters 2 and 3, respectively.

Let's think of an entity type "student". A student has:

a last name consisting of up to 128 characters (this cannot contain a missing value),
a unique social security number of length 9, consisting only of integers,
a phone number of fixed length 12, consisting of numbers and characters (but some students don't have one).

Given the above description of a student entity, create a table students with the correct column types.
Add a PRIMARY KEY for the social security number ssn.

Note that there is no formal length requirement for the integer column. The application would have to make sure it's a correct SSN!

Exercise

Test your knowledge before advancing

Instructions