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Supabase · Error fix

Fix PGRST200: Could not find a relationship in the schema cache

01 What the error says

response

{
  "code": "PGRST200",
  "message": "Could not find a relationship between 'books' and 'authors' in the schema cache",
  "details": "Searched for a foreign key relationship between 'books' and 'authors' in the schema 'public', but no matches were found."
}

A query like supabase.from('books').select('title, authors(name)') asks the Data API to join through a foreign key. It doesn't guess joins from column names: author_id alone isn't enough.

02 Check which foreign keys exist

check.sql

select conrelid::regclass as from_table, confrelid::regclass as to_table, conname
from pg_constraint
where contype = 'f' and connamespace = 'public'::regnamespace
order by 1;

03 Add the foreign key

migration.sql

alter table public.books
  add constraint books_author_id_fkey
  foreign key (author_id) references public.authors(id);

notify pgrst, 'reload schema';

The referenced column must be a primary key or unique, otherwise Postgres refuses the constraint (there is no unique constraint matching given keys).

04 Two keys between the same tables: PGRST201

If books has both author_id and editor_id pointing to authors, the embed is ambiguous and you get PGRST201, whose hint lists the options. Name the foreign key:

// pick the relationship by constraint name
supabase.from('books').select('title, author:authors!books_author_id_fkey(name)')

05 Found, but the joined rows are empty

That's RLS, not the relationship: the embedded table has its own policies, and rows the caller can't see come back as null or an empty array. Check the SELECT policy on the joined table.

FAQ