Database
db={items:[{id:38219388214034,status:"inStock",category:"Food",subCategory:"Sweet"},{id:18371917455611,status:"pending",category:"Accessories",subCategory:"Other"},{id:38219388214035,status:"inStock",category:"Food",subCategory:"Sweet"},{id:38219388214037,status:"pending",category:"Food",subCategory:"Sweet"},{id:38219388214032,status:"pending",category:"Food",subCategory:"Other"}]}
Query
db.items.aggregate([{$group:{_id:{subCategory:"$subCategory",category:"$category"},totalCount:{$sum:1},pending:{$sum:{$cond:[{$eq:["$status","pending"]},1,0]}},inStock:{$sum:{$cond:[{$eq:["$status","inStock"]},1,0]}},outOfStock:{$sum:{$cond:[{$eq:["$status","outOfStock"]},1,0]}}}}])