DocumentDb SELECT with JOIN not returning anything - azure

Question

My document in DocumentDb looks like this:
{
"id": 123,
"timers":
{
"projectTimer":
{
"id": 234,
"name": "My Project",
"startTime": "10:35 AM"
},
"taskTimer":
{
"id": 789,
"name": "My Task",
"startTime": "10:45 AM"
}
}
}
The key points here are:
"timers" is an object -- NOT an array
The sub-objects are also set i.e. "projectTimer" and "taskTimer"
If I set my SELECT statement to the following, it works by giving me both projectTimer and taskTimer sub-objects
SELECT c.timers
FROM Collection c
WHERE c.id = 123
But the following returns nothing. I don't understand why because it seems like a really simple JOIN:
SELECT t.projectTimer
FROM Collection c
JOIN t IN c.timers
WHERE c.id = 123
Any idea where I'm making a mistake?

Answer 1

The issue is that you're trying to do a JOIN on something that's not an array.
If, instead, you reworked your document slightly:
{
"id": "123",
"timers": [
{
"projectTimer": {
"id": 234,
"name": "My Project",
"startTime": "10:35 AM"
}
},
{
"taskTimer": {
"id": 789,
"name": "My Task",
"startTime": "10:45 AM"
}
}
],
}
You'd then be able to do a JOIN like:
select value t
from collection c
join t in c.timers
where c.id = "123"
Which would return each of the timers in the array:
[
{
"projectTimer": {
"id": 234,
"name": "My Project",
"startTime": "10:35 AM"
}
},
{
"taskTimer": {
"id": 789,
"name": "My Task",
"startTime": "10:45 AM"
}
}
]
Note the use of VALUE in the query, to strip away the containing t variable.