Schema.Table.Column.. a problem?

Question

In Oracle 8.1.7.4.1:
SQL> create table trial ( a number);
Table created.
SQL> insert into trial (a) values (10);
1 row created.
SQL> commit;
Commit complete.
SQL> select sysadm.trial.a from trial;
select sysadm.trial.a from trial
ERROR at line 1:
ORA-00904: invalid column name
SQL> select sysadm.trial.a from sysadm.trial;
A
10
SQL> select trial.a from trial;
A
10
SQL> select trial.a from sysadm.trial;
A
10
SQL> show user
USER is "SYSADM"
Question:
>>>>>>
SQL> select sysadm.trial.a from trial;
>>>>>>
Why does this select fail even when I am firing the statement with the same database USER?

Answer 1

SELECT sysadm.trial.a FROM sysadm.trial and
SELECT trial.a FROM trial
Works for the same reason that SELECT t.a FROM trial t does, you are selecting alias.column. By default, Oracle uses the table name as given in the FROM clause as the alias for that table. Therefore, you can use that alias anywhere else in the query.
SELECT trial.a FROM sysadm.trial
Works because Oracle is smart enough to recognize that the owner is not neccessary, and in fact, Oracle generally ignores the owner qualification in SELECT lists viz.
SQL> SHOW USER
USER is "OPS$ORACLE"
SQL> CREATE TABLE t (id NUMBER);
Table created.
SQL> INSERT INTO t VALUES (1);
1 row created.
SQL> COMMIT;
Commit complete.
SQL> GRANT CONNECT, RESOURCE TO u IDENTIFIED BY test;
Grant succeeded.
SQL> GRANT SELECT ON t TO u;
Grant succeeded.
SQL> CONNECT u/test;
Connected.
SQL> CREATE TABLE t (id number);
Table created.
SQL> INSERT INTO t VALUES(2);
1 row created.
SQL> COMMIT;
Commit complete.
SQL> SELECT ops$oracle.t.id, t.id
  2  FROM ops$oracle.t, t
  3  /
SELECT ops$oracle.t.id, t.id
ERROR at line 1:
ORA-00918: column ambiguously definedBut Oracle can use it when neccessary to unambiguously identify a column:
SQL> SELECT ops$oracle.t.id, u.t.id
  2  FROM ops$oracle.t, u.t;
        ID         ID
         1          2Since Oracle mostly does not care about the table owner in select lists, it is no surprise that it won't add the owner when you do:
select sysadm.trial.a from trial
HTH
John