How to use a JOIN inside a CASE expression?

I have four tables like this: **company**: | id | companyContactID | customerID | companyTeamID | | -------- | ---------------- | ---------- | ------------- | | 1 | 12 | 21 | 54 | | 2 | 14 | 12 | 78 | **document_associated_company**: | id | companyID | documentID | | -------- | --------- | ---------- | | 1 | 2 | 98 | | 2 | 1 | 12 | **document** | id | documentTypeID | | -------- | -------------- | | 98 | 67 | | 12 | 87 | **document_type** | id | name | | -------- | ------ | | 67 | NDA | | 87 | SOW | And I have an SQL query like this:

SELECT CASE
  WHEN company."customerID" IS NOT NULL THEN 'customer'
  WHEN company."companyContactID" IS NOT NULL THEN 'lead'
  WHEN company."companyTeamID" IS NOT NULL THEN 'lead'
  ELSE 'company'
  END AS status
FROM   company;

I have used a CASE expression here to create a new column named status. Basically, according to the several conditions I set the status of the company. Additionally, I need to check whether the company has a document attached with a certain type. For example, if the company have a document with the type NDA attached, then its status would be 'active'. For this I would have to put several JOIN statements. Any idea how to integrate this into the CASE expression? **Expected result:** | status | | ------ | | active | | customer |