Pseudo-columns
A pseudocolumn behaves like a column of a table but it is not really stored in the table. The Selection can be done from Pseudocolumns but DML operations are not possible. The Pseudocolumns are listed as follows:
• ROWNUM
• ROWID
• LEVEL
• CURRVAL
• NEXTVAL
(CURRVAL and NEXTVAL are dealt in the chapter on Sequences.)