This illustration is a tree depicting the execution plan for the statement in the preceding text. Step 1, Concatenation, is a clear box that branches to Step 2, Table Access (by rowid) emp, and Step 4, Table Access (by rowid) emp, which are both shaded boxes. Step 2 branches to Step 3, Index (range scan) deptno_index, a shaded box, and Step 4 branches to Step 5, Index (range scan) job_index, a shaded box. For an explanation of the meaning of clear and shaded boxes, see the "Steps in the Execution Plan" section in Chapter 1.