Oracle db wrong result on subquery error

Question

Hi,
I work with Oracle databases up to 10g and I found an error and couldn’t find any documentation about it yet. Perhaps you can help me.
The error is quite easy to replicate. If you run the following query adapting the parameters you should get a result, the problem is that you should only get an error!
select * from user_tab_columns
where table_name in
select table_name from <TABLE_B>
Parameter: TABLE_B
Description: This should be an existing table of the schema which doesn’t have any table_name field.
As I said, the sub-query is wrong, so if you try to run it separately it fails. The problem is when you run both together because, if the link field has the same name, it returns all values of the table in the outer query.
Do you know if this is solved in 11g or in a specific patch of 10g?
Thanks in advance for your interest.
Best regards,
Leo ([email protected])

Answer 1

user6396183 wrote:
I don't think a query whose inner query evaluates to ORA-00904 'Invalid identifier' should return anything, it's not logic. To me this is a bug.
If you execute the following query it will retrieve all records from the outer table when it should only return an exception as the inner query can not be evaluated at all.
select * from user_tab_columns
where table_name in (select table_name from user_role_privs);You still did not get it. Yes inner query by itself results in ORA-00904 'Invalid identifier' only if you execute it independently:
select table_name from user_role_privsOracle parser tries to figure out what table_name is. It is not a literal, therefore it concludes it is an identifier. Now the only table in FROM list is user_role_privs and it has no such column. Then parser checks if such function exists and it does not, etc... At the end ORA-00904 'Invalid identifier' is raised. However, look what happens if you issue it as a sub_query:
select * from user_tab_columns
where table_name in (select table_name from user_role_privs);Again, Oracle parser tries to figure out what table_name is. It is not a literal, therefore it concludes it is an identifier. Now the only table in FROM list is user_role_privs and it has no such column. Now, parser realizes it is a subquery and table_name can be a correlated name. So it checks main query FROM clause list and guess what - table user_tab_columns has a column table_name. So what subquery means is select a row from table user_tab_columns, which will give as some column table_name value and then use that value in subquery, get results and compare it with same table_name value. Now, I hope, you can see that no error should be raised. And, if user_role_privs is not empty, query will return every row in user_tab_columns. If user_role_privs is empty, query will not return any rows. But again, error is neither raised nor should be raised.
SY.