This illustration is a tree depicting the execution plan for the statement in the preceding text. Step 1, View two_emp_tables, is a clear box that branches to Step 2, Projection, a clear box. Step 2 branches to Step 3, Sort (unique), a clear box. Step 3 branches to Step 4, Union-All, a clear box. Step 4 branches to Step 5, Table Access (full) emp1, and Step 6, Table Access (full) emp2, which are both shaded boxes. For an explanation of the meaning of clear and shaded boxes, see the "Steps in the Execution Plan" section in Chapter 1.