PostgreSQL , Select from 2 tables, but only the latest element from table 2

Question

Hey, I have 2 tables in PostgreSql:

1 - documents: id, title
2 - updates: id, document_id, date

and some data:

documents:

Answer 1

select *
from documents
left join updates
  on updates.document_id=documents.id
  and updates.date=(select max(date) from updates where document_id=documents.id)
where documents.id=?;

It has the some advantages over previous answers:

• you can write document_id only in one place which is convenient;
• you can omit where and you'll get a table of all documents and their latest updates;
• you can use more broad selection criteria, for example where documents.id in (1,2,3).

You can also avoid a subselect using group by, but you'll have to list all fields of documents in group by clause:

select documents.*, max(date) as max_date
  from documents
  left join updates on documents.id=document_id
  where documents.id=1
  group by documents.id, title;