슈도컬럼
SQL> select deptno, rowid as c1 from dept;
DEPTNO C1
------------ -------------------
10 AAAvKUAAPAAA/F7AAA
20 AAAvKUAAPAAA/F7AAB
30 AAAvKUAAPAAA/F7AAC
40 AAAvKUAAPAAA/F7AAD