Rowid and urowid datatypes

Question

I'm writing an exercise to learn more about different datatypes and am confused about the use of and difference between rowid and urowid. As I understand it using rowid should only be done when writing for backwards compatibility, and urowid should be used for new coding. I'm working in 9.2.0.1.0, so I assume I should use urowid.
The following code returns an error (shown below). Anyone know why this is happenning?
create or replace function lrnvrbls
return varchar2
is
v_rowid urowid;
v_data varchar2(100);
select rowid
into v_rowid
from mytable
where rownum = 10 -- 10 is just a number I chose
execute immediate
'select mycolumn ' ||
'from mytable ' ||
'where rowid = ' ||
v_rowid
into v_data;
return v_data;
end;
SQL>select lrnvrbls from dual;
select lrnvrbls from dual
ORA-00904: "AAAHCAAAMAAAADVAAI": invalid identifier
I've tried using both ROWID and UROWID datatypes with no luck. Also tried CHARTOROWID and ROWIDTOCHAR and failed the same way.
Anybody understand how to use this?

Answer 1

A single datatype called the universal rowid, or UROWID, supports both logical
and physical rowids, as well as rowids of foreign tables such as non-Oracle
tables accessed through a gateway.
A column of the UROWID datatype can store all kinds of rowids. The value of the
COMPATIBLE initialization parameter must be set to 8.1 or higher to use UROWID
columns.
DROP TABLE mytable
CREATE TABLE mytable
AS SELECT owner mycolumn FROM all_tables
WHERE rownum < 100
CREATE OR REPLACE
FUNCTION lrnvrbls
RETURN varchar2
IS
v_rowid urowid;
v_data varchar2(100);
strSQL varchar2(255);
BEGIN
select rowid
into v_rowid
from mytable
where rownum = 1;
strSQL := 'select mycolumn from mytable where rowid = '''||v_rowid ||'''';
execute immediate strSQL into v_data;
return v_data;
END lrnvrbls;
SELECT lrnvrbls FROM DUAL
DROP FUNCTION lrnvrbls
DROP TABLE mytable
COMMIT
16:39:37 SQL> DROP TABLE mytable
16:39:39 2 /
Table dropped.
Elapsed: 00:00:00.00
16:39:39 SQL> --
16:39:39 SQL> CREATE TABLE mytable
16:39:39 2 AS SELECT owner mycolumn FROM all_tables
16:39:39 3 WHERE rownum < 100
16:39:39 4 /
Table created.
Elapsed: 00:00:00.00
16:39:39 SQL> --
16:39:39 SQL> CREATE OR REPLACE
16:39:39 2 FUNCTION lrnvrbls
16:39:39 3 RETURN varchar2
16:39:39 4 IS
16:39:39 5 --
16:39:39 6 v_rowid urowid;
16:39:39 7 v_data varchar2(100);
16:39:39 8 strSQL varchar2(255);
16:39:39 9 --
16:39:39 10 BEGIN
16:39:39 11 --
16:39:39 12 select rowid
16:39:39 13 into v_rowid
16:39:39 14 from mytable
16:39:39 15 where rownum = 1;
16:39:39 16 --
16:39:39 17 strSQL := 'select mycolumn from mytable where rowid = '''||v_rowid ||'''';
16:39:39 18 --
16:39:39 19 execute immediate strSQL into v_data;
16:39:39 20 --
16:39:39 21 return v_data;
16:39:39 22 --
16:39:39 23 END lrnvrbls;
16:39:39 24 /
Function created.
Elapsed: 00:00:00.00
16:39:39 SQL> --
16:39:39 SQL> SELECT lrnvrbls FROM DUAL
16:39:39 2 /
LRNVRBLS
SYS
Elapsed: 00:00:00.00
16:39:39 SQL> --
16:39:39 SQL> DROP FUNCTION lrnvrbls
16:39:39 2 /
Function dropped.
Elapsed: 00:00:00.01
16:39:40 SQL> DROP TABLE mytable
16:39:40 2 /
Table dropped.
Elapsed: 00:00:00.00
16:39:40 SQL> COMMIT
16:39:40 2 /
Commit complete.
Elapsed: 00:00:00.00
16:39:40 SQL>
*/