Read Inconsistency?

Riddle me this: Can an object exist in all_objects before it is created?
Well no, of course not.
I was under the assumption that if you create a table with a select-statement, a CTAS – Create Table As Select – that the select was executed prior to the creation of the table. Read Consistency dictates that the result set returned by a Select statement, returns the values as of that particular moment in time.

To demonstrate this Tom Kyte has an example similar to this:

SQL&gt; var rc refcursor<br />SQL&gt; create table t<br />  2  as<br />  3  select *<br />  4    from dual<br />  5  /<br /><br />Table created.<br /><br />SQL&gt; exec open :rc for select * from t<br /><br />PL/SQL procedure successfully completed.<br /><br />SQL&gt; delete from t<br />  2  /<br /><br />1 row deleted.<br /><br />SQL&gt; commit<br />  2  /<br /><br />Commit complete.<br /><br />SQL&gt; print<br /><br />D<br />-<br />X<br /><br />SQL&gt;<br />

The shortest possible script to demonstrate Read Consistency. The result you see after the Delete followed by a Commit, are returned by the Ref Cursor, which was executed prior to the delete.

Odd or at least Remarkable?

Isn’t this odd then?

SQL&gt; drop table t purge<br />  2  /<br /><br />Table dropped.<br /><br />SQL&gt; select owner, object_name<br />  2    from all_objects<br />  3   where owner = 'ALEX'<br />  4     and object_name = 'T'<br />  5  /<br /><br />no rows selected<br /><br />SQL&gt; create table t<br />  2  as<br />  3  select *<br />  4    from all_objects<br />  5  /<br /><br />Table created.<br /><br />SQL&gt; select owner, object_name<br />  2    from t<br />  3   where owner = 'ALEX'<br />  4     and object_name = 'T'<br />  5  /<br /><br />OWNER                          OBJECT_NAME<br />------------------------------ -----------<br />ALEX                           T<br /><br />SQL&gt;<br />

How is it possible that an entry is alread present in the newly created Table T, which should be a copy of ALL_OBJECTS? Apparently, when you create a table, an entry in the datadictionary is created prior to executing the Select-statement…. strange, don’t you think?
That goes to show it, the datadictionary is "special".