PostgreSQL: SQL script to get a list of all tables that has a particular column as foreign key

Question

I\'m using PostgreSQL and I\'m trying to list all the tables that have a particular column from a table as a foreign-key/reference. Can this be done? I\'m sure this information

Answer 1

The other solutions are not guaranteed to work in postgresql, as the constraint_name is not guaranteed to be unique; thus you will get false positives. PostgreSQL used to name constraints silly things like '$1', and if you've got an old database you've been maintaining through upgrades, you likely still have some of those around.

Since this question was targeted AT PostgreSQL and that is what you are using, then you can query the internal postgres tables pg_class and pg_attribute to get a more accurate result.

NOTE: FKs can be on multiple columns, thus the referencing column (attnum of pg_attribute) is an ARRAY, which is the reason for using array_agg in the answer.

The only thing you need plug in is the TARGET_TABLE_NAME:

select 
  (select r.relname from pg_class r where r.oid = c.conrelid) as table, 
  (select array_agg(attname) from pg_attribute 
   where attrelid = c.conrelid and ARRAY[attnum] <@ c.conkey) as col, 
  (select r.relname from pg_class r where r.oid = c.confrelid) as ftable 
from pg_constraint c 
where c.confrelid = (select oid from pg_class where relname = 'TARGET_TABLE_NAME');

If you want to go the other way (list all of the things a specific table refers to), then just change the last line to:

where c.conrelid = (select oid from pg_class where relname = 'TARGET_TABLE_NAME');

Oh, and since the actual question was to target a specific column, you can specify the column name with this one:

select (select r.relname from pg_class r where r.oid = c.conrelid) as table, 
       (select array_agg(attname) from pg_attribute 
        where attrelid = c.conrelid and ARRAY[attnum] <@ c.conkey) as col, 
       (select r.relname from pg_class r where r.oid = c.confrelid) as ftable 
from pg_constraint c 
where c.confrelid = (select oid from pg_class where relname = 'TARGET_TABLE_NAME') and 
      c.confkey @> (select array_agg(attnum) from pg_attribute 
                    where attname = 'TARGET_COLUMN_NAME' and attrelid = c.confrelid);