1. Add a table-level PRIMARY KEY constraint to the EMP table on the ID column. The constraint
   should be named at creation. Name the constraint my_emp_id_pk

2. Create a PRIMARY KEY constraint to the DEPT table using the ID column. The constraint
   should be named at creation. Name the constraint my_dept_id_pk.

3. Add a column DEPT_ID to the EMP table. Add a foreign key reference on the EMP table that
   ensures that the employee is not assigned to a nonexistent department. Name the constraint
   my_emp_dept_id_fk.

4. Confirm that the constraints were added by querying the USER_CONSTRAINTS view. Note the
   types and names of the constraints. Save your statement text in a file called lab10_4.sql.

5. Display the object names and types from the USER_OBJECTS data dictionary view for the EMP
   and DEPT tables. Notice that the new tables and a new index were created.

6. Modify the EMP table. Add a COMMISSION column of NUMBER data type, precision 2, scale 2.
   Add a constraint to the commission column that ensures that a commission value is greater than
   zero.