What are the pseudo columns in oracle, rowid, etc.

Why rowid are all empty

The test statement is as follows:

select rowid from dual; 

Found no results. Why is this?
Because the tool used does not support this field, just add a column alias.

The revised sentence is as follows:

select rowid as rowid_p from dual;

Sure enough, there are results.

What are the pseudocolumns

CURRVAL, LEVEL, NEXTVAL, ROWID, and ROWNUM.