Returning VALUE or NULL in Azure Cosmos DB subquery - azure-cosmosdb

Question

The structure of the Person document I store in Azure Cosmos DB looks like this:
{
"id": "some-id",
"firstName": "John",
"lastName": "Doe",
"emails": [
{
"id": "email1",
"email": "test#testsite.com",
"isPrimary": true
},
{
"id": "email2",
"email": "test2#testsite.com",
"isPrimary": false
}
]
},
{
"id": "some-other-id",
"firstName": "Jane",
"lastName": "Doe",
"emails": []
}
I'm trying to return the basic info of a person, including his/her primary email if they have one and NULL for email if there isn't a primary email.
This is the SQL statement I'm using but it's not returning Jane Doe at all because "I think" the JOIN is making the email required data.
SELECT c.id, c.firstName, c.lastName, email
FROM c JOIN (SELECT e.email FROM e IN c.emails WHERE e.isPrimary = true) AS email
I also tried the following but that doesn't Jane Doe at all.
SELECT c.id, c.firstName, c.lastName, e.email
FROM c JOIN e IN c.emails
WHERE e.isPrimary = true
I thought the following worked but that also seems to filter out some documents where there's an email but not a primary one.
SELECT c.id, c.firstName, c.lastName, e.email
FROM c JOIN e IN c.emails
WHERE ARRAY_LENGTH(c.emails) = 0 OR e.isPrimary = true
Just to reiterate the requirements: I want ALL persons. If the person has one or more emails and one is the primary one, I want to include only the primary email in the result. If the person doesn't have any emails or has emails but not a primary one, I still want the person in the results but email should be NULL for that particular person.
It's easy to do a SELECT * FROM c but I only want to get the primary email if the person has one or a NULL if they don't.

Answer 1

SELECT c.firstName, c.lastName,
ARRAY(SELECT VALUE e.email FROM e in c.emails WHERE e.isPrimary = true or ARRAY_LENGTH(c.emails) = 0) as email
FROM c