I have an assignment where I have to list out all the employees in europe. Now, I know how to do this but I've hit a roadblock. I need to figure out which country a location is in, which would be easy except I keep getting the same error.

Here's a nice example:

Code:
SQL> select * from hr.countries;

CO COUNTRY_NAME                              REGION_ID
-- ---------------------------------------- ----------
AR Argentina                                         2
AU Australia                                         3
BE Belgium                                           1
BR Brazil                                            2
CA Canada                                            2
CH Switzerland                                       1
CN China                                             3
DE Germany                                           1
DK Denmark                                           1
EG Egypt                                             4
FR France                                            1

... *snip*

25 rows selected.

SQL> select CO from hr.countries;
select CO from hr.countries
       *
ERROR at line 1:
ORA-00904: invalid column name
CO is clearly a column, yet it refuses to be used in a statement?? How can I select this column?