select
	u.id as UserID,
	u.DisplayName,
	u.Username,
	u.Capacity as Capacity,
	count(cq.chatid) as ActiveChats,
	case when count(cq.chatid) >= u.Capacity then 1 else 0 end as AtCapacity
from
	users u
left join
	ChatQueueItems cq
on
	cq.UserID = u.ID
left join
	Chats c
on
	c.ID = cq.ChatID
and
	c.[Status] in (0,1) -- 0 = awaiting pickup, 1 = active
where
	u.[online] = 1
group by
	u.id,
	u.DisplayName,
	u.Username,
	u.capacity