How do I use OData Expand like a SQL join?

I'm trying to figure out how to accomplish the equivalent of:

select *
from Users u
inner join Comments c on c.UserId = u.Id
where Id = 1569

(table aliases for better sql readability)

...on the StackOverflow OData endpoint. How would this url be constructed? I'm looking at the documentation for Expand at OData.org and I would have thought it'd look something like:

https://odata.sqlazurelabs.com/OData.svc/v0.1/rp1uiewita/StackOverflow/Users?$Expand=Comments&$filter=UserId eq 1569 but isn't right.

In Linq, it would be this (I think), but Join isn't supported:

Users.Where(u=>u.Id==1569).Join(Comments, u=>u.Id, c=>c.UserId, (a,b)=>a.Id==b.UserId)

I don't need to figure this out in Linq strictly, I'm just trying to figure out how to construct the query url. Basically, how can I translate the SQL join predicate to an OData url and do this in one call?