Globale temporary table

Question

I've created a global temporary table as the following:
Create global temporary table temp as select * from emp;
Doesn't that mean it create temp table as the structure of table emp and inserted the same rows as emp's table rows?
Because when I tried to select from temp after creating it, it retrieves no rows.
Thanks in advance

Answer 1

The default mechanism for 'create global temporary table'
is that delete rows on commit.
In your case, you are really executing the command
'Create global temporary table temp
on commit delete rows as select * from emp;'
It should be:
'Create global temporary table temp
on commit preserve rows as select * from emp;'
Here is an example.
SQL> ed
Wrote file afiedt.buf
  1   Create global temporary table temp
  2*  on commit delete rows  as select * from user_objects
SQL> /
Table created.
SQL> select count(1) from temp;
  COUNT(1)
         0
SQL> Create global temporary table temp1
  2  on commit preserve rows as select * from user_objects;
Table created.
SQL> select count(1) from temp1;
  COUNT(1)
       549