Basic NOT EXISTS query not returning any results

Question

DB Version: 10gR2
One of our tables in the test schema is having less number of columns than the PROD shema.
To determine which are missing columns in this table in Test schema i did the following.
-----In Test Schema
CREATE TABLE XYZ2
(COL1 NUMBER);        ----------only one column
SQL > CREATE TABLE tables_test_list AS SELECT TABLE_NAME,COLUMN_NAME FROM USER_TAB_COLS;
Table created.--- In the prod schema
SQL> CREATE TABLE XYZ2
  2  (COL1 NUMBER,
  3  COL2 NUMBER       ----------- same table name with an extra column
  4  );
Table createdAnd from the PROD schema i execute the following SQL to determine what are the columns that are missing in the TEST schema
select column_name from User_Tab_Cols  outer
where table_name='XYZ2'
and not exists (select 1 from TEST_SCHEMA.tables_test_list inner where outer.TABLE_NAME=inner.TABLE_NAME )But the above query is not returning any results. Any idea why?

Answer 1

Actually, the example from the link I posted earlier:
[email protected]> (
  2  select 'IN T1, NOT T2', column_name,data_type,data_length
  3    from user_tab_columns
  4   where table_name = 'T1'
  5  MINUS
  6  select 'IN T1, NOT T2', column_name,data_type,data_length
  7    from user_tab_columns
  8   where table_name = 'T2'
  9  )
10  UNION ALL
11  (
12  select 'IN T2, NOT T1', column_name,data_type,data_length
13    from user_tab_columns
14   where table_name = 'T2'
15  MINUS
16  select 'IN T2, NOT T1', column_name,data_type,data_length
17    from user_tab_columns
18   where table_name = 'T1'
19  )
20  /