我是新手到蒙戈,我試圖通過值取組中的子文檔,並具有蒙戈集合結構,如:如何組蒙戈子文件
{
"_id" : ObjectId("589d4e4b270f8b1635d400b1"),
"myShopId" : 439,
"products" : [
{
"productId" : "1234",
"productName" : "sambarpowder 500 gm",
"productCategory" : "masala",
"mrp" : "90",
"_id" : ObjectId("589d595f6da20b72fe006ea9")
},
{
"productId" : "5678",
"productName" : "moong dhal 200 gms",
"productCategory" : "dhal",
"mrp" : "38 ",
"_id" : ObjectId("589d595f6da20b72fe006eaa")
},
{
"productId" : "5678",
"productName" : "moong dhal 200 gms",
"productCategory" : "dhal",
"mrp" : "38 ",
"_id" : ObjectId("589d595f6da20b72fe006eaa")
}
],
"isAlive" : 1,
"__v" : 3
}
在這裏,我想這樣做在這一組中。 用於例如在MySQL:
select productCategory from products where shopId = '439' groupby productCategory
我怎樣才能通過蒙戈子文件
My Expected output is like :
category : [{
productCategory : masala
_id : ObjectId("589d595f6da20b72fe006ea9")
},
{
productCategory : dhal
_id : ObjectId("589d595f6da20b72fe006eaa")
}
]
我已經試過這樣db.shopProductDetails.group({ 「鑰匙」:{ 「products.productCategory」:真 }, 「初始」:{}, 「減少「:function(obj,prev){}, 」cond「:{ 」shopId「:」439「 } }); – karthik
但我得到空元素 – karthik
該組命令變體已棄用。改用'$ group'彙總。 https://docs.mongodb.com/manual/reference/operator/aggregation/group/。對於整套管道階段。 https://docs.mongodb.com/manual/reference/operator/aggregation-pipeline/ – Veeram