Data Dictionary.. Help Please

Question

I have to create this query for my college course. I need help. I have half of the query, I think. Need another join clause in the from statement for the views, not sure what to do. Any help will be appreciated! Thank you!
Create and execute a single query of the Oracle data dictionary to display all foreign key constraints in the HR schema. Note that foreign key constraints are constraint type 'R'. For each constraint list the constraint type, constraint name, the referencing table name, the referencing column position(s), the referencing column name(s), the referenced constraint name (i.e. the other table's primary key constraint name), the referenced table, and the referenced column(s). Sort your results by constraint name, table_name, and position.
HINTS: You will need two different data dictionary views for this query. One of the views will need to be mentioned twice in the FROM clause, and therefore you will need two different aliases. With this arrangement you will also need two join conditions.
This is what i have so far...
SELECT uc.constraint_type, uc.constraint_name, uc.table_name, r_constraint_name,
ucc.table_name, ucc.position, ucc.column_name, ucc.constraint_name
FROM user_constraints uc JOIN user_cons_columns ucc
ON uc.table_name= ucc.table_name
AND uc.constraint_name= ucc.constraint_name
WHERE constraint_type= 'R'
AND r_constraint_name IN
(SELECT constraint_name
FROM all_constraints
WHERE constraint_type
IN ('P','U')
AND table_name= 'hr')
ORDER BY uc.constraint_name, ucc.table_name,ucc.position;

Answer 1

Ok, you have the correct two dictionary views (assuming you are logged in as HR), now you need to figure out which one is needed twice. As a hint, you have the required join columns for the doubled dictionary view in the single use dictionary view.
A couple of comments on the code you have posted so far.
The predicate:
r_constraint_name IN (SELECT constraint_name
                      FROM all_constraints
                      WHERE constraint_type IN ('P','U') AND
                            table_name= 'hr')is unnecessary since by definition, if the constraint type is R, then the r_constraint_column will point to a P (primary key) or U (unique key) constraint.
By default, all objects in Oracle are stored in the dictionary views in upper case, so when you query a value you need to use upper case for the literal.
Again, assuming that you are logged in as HR, then the user_xxx views will only show objects that belong to the HR schema, so there is no need to qualify anything with an owner.
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John