Figure 6�1 shows a base table named "employees," containing four rows of employee data in seven columns. The seven columns, left to right, are employee_id, last_name, job_id, manager_id, hire_date, salary, and department id, abbreviated dept_id. The four rows are for employees with ids 203, 204, 205, and 206, with data in each of the other columns as well. Below the base table in this figure is a view called "staff," derived from the base "employees" table. However, the view shows only five of the columns in the base table: employee_id, last_name, job_id, manager_id, and dept_id. The base table columns labeled hire-date and salary are omitted. The figure has vertical lines connecting the view columns with their source columns in the base table. These lines illustrate both where the information comes from and the fact that two columns of the base table have no representation in the view.