PostgreSQ 查询表外键依赖关系

（1）查询当前表被哪些子表所依赖

SELECT x.table_name, x.column_name FROM information_schema.key_column_usage x  #key_column_usage是系统列信息表
INNER JOIN 
  (SELECT t.relname, a.conname  
  FROM pg_constraint a                                                 #pg_constraint是系统所有约束表
  INNER JOIN pg_class ft  ON ft.oid = a.confrelid  
  INNER JOIN pg_class t  ON t.oid = a.conrelid WHERE a.contype = 'f' 
  AND a.confrelid = 
    (select e.oid   from pg_class e  where e.relname = 'auth_user')     #'auth_user'是所需要的查询表
 ) tp 
ON (x.table_name = tp.relname AND x.constraint_name = tp.conname);

查询结果

（2）查询当前表依赖哪些表

  SELECT tc.constraint_name,tc.table_name, kcu.column_name,
		ccu.table_name AS foreign_table_name,
		ccu.column_name AS foreign_column_name, 
		tc.is_deferrable,tc.initially_deferred 
  FROM information_schema.table_constraints AS tc 
		JOIN information_schema.key_column_usage AS kcu ON tc.constraint_name = kcu.constraint_name 
		JOIN information_schema.constraint_column_usage AS ccu ON ccu.constraint_name = tc.constraint_name 
  WHERE constraint_type = 'FOREIGN KEY' AND tc.table_name='auth_user_user_permissions';        # 是所需要查询的表