Query a Table's Foreign Key relationships

Question

For a given table 'foo', I need a query to generate a set of tables that have foreign keys that point to foo. I'm using Oracle 10G.

Solution 1

This should work (or something close):

select table_name
from all_constraints
where constraint_type='R'
and r_constraint_name in 
  (select constraint_name
  from all_constraints
  where constraint_type in ('P','U')
  and table_name='<your table here>'); 

Solution 2

The following statement should give the children and all of their descendents. I have tested it on an Oracle 10 database.

SELECT  level, main.table_name  parent,
    link.table_name child
FROM    user_constraints main, user_constraints link    
WHERE   main.constraint_type    IN ('P', 'U')
AND link.r_constraint_name  = main.constraint_name
START WITH main.table_name  LIKE UPPER('&&table_name')
CONNECT BY main.table_name = PRIOR link.table_name
ORDER BY level, main.table_name, link.table_name

Solution 3

Here's how to take Mike's query one step further to get the column names from the constraint names:

select * from user_cons_columns
where constraint_name in (
  select constraint_name 
  from all_constraints
  where constraint_type='R'
  and r_constraint_name in 
    (select constraint_name
    from all_constraints
    where constraint_type in ('P','U')
    and table_name='<your table name here>'));

Solution 4

I know it's kinda late to answer but let me answer anyway. Some of the answers above are quite complicated hence here is a much simpler take.

SELECT a.table_name child_table, a.column_name child_column, a.constraint_name, 
b.table_name parent_table, b.column_name parent_column
FROM all_cons_columns a
JOIN all_constraints c ON a.owner = c.owner AND a.constraint_name = c.constraint_name
join all_cons_columns b on c.owner = b.owner and c.r_constraint_name = b.constraint_name
WHERE c.constraint_type = 'R'
AND a.table_name = 'your table name'

Solution 5

link to Oracle Database Online Documentation

You may want to explore the Data Dictionary views. They have the prefixes:

• User
• All
• DBA

sample:

select * from dictionary where table_name like 'ALL%' 

---

Continuing Mike's example, you may want to generate scripts to enable/disable the constraints. I only modified the 'select' in the first row.

select  'alter table ' || TABLE_NAME || ' disable constraint ' || CONSTRAINT_NAME || ';'
from all_constraints
where constraint_type='R'
and r_constraint_name in 
  (select constraint_name
  from all_constraints
  where constraint_type in ('P','U')
  and table_name='<your table here>');

View more solutions

Comments

[Sean]

This article may help: http://www.databasejournal.com/features/oracle/article.php/3‌​665591

[Sten Vesterli]

If you just need this info in order to drop the table, you can also use DROP TABLE xx CASCADE CONSTRAINTS

[focusHard]

nice use of hierarchical retrieval. However when you have tables with self referencing foreign keys, it will generate error.

[Tom]

This is the greatest thing ever. You just need to change the 'U' to 'R' for newer versions of Oracle.

[Tom]

@focusHard, I believe that adding AND main.table_name <> link.table_name to the where clause will prevent that error.

[Ravi Wallau]

I think this works better: <pre> select a.table_name child_table, a.column_name child_column, a.constraint_name, b.table_name parent_table, b.column_name parent_column, a.position from user_cons_columns a join user_constraints c on a.owner = c.owner and a.constraint_name = c.constraint_name join user_cons_columns b on c.owner = b.owner and c.r_constraint_name = b.constraint_name and a.position = b.position where c.constraint_type = 'R' order by a.constraint_name, a.table_name, a.column_name, b.table_name, b.column_name

[Gh61]

When the foreing key is over multiple columns, this query returns invalid results.