how to retrive null data from Left Join in mysql when right table has no matching row?

Question

I have two tables like these: (Docs)

Id	Name
1	Doc1
2	Doc2

and

(Signs)

Id	personId	docId	SignedAt
1	1	1	2023-01-01
2	3	2	2023-01-02

So I want to get details of docs for each user. for instance I need a list to show that user with Id = 1 like this:

(result)

DocId	signedAt
1	2023-01-01
2	null

I tried Left Join like below:

SELECT * from docs
LEFT JOIN Signs on docid = docs.id 
where Signs.personId = 1 || Signs.personId is null;

but it just returns the first line of the result table. how could I generate my desired result?

Answer 1

SELECT t1.id, t2.signed_at
FROM docs t1
LEFT JOIN signs t2 ON t1.id = t2.doc_id AND t2.person_id = 1