获取同一文档mongodb中的$ sum项

Question

/* 1 */
{
    "_id" : ObjectId("5941240cdc8dd12a183337b0"),
    "item" : ObjectId("593e700d9f34350aac73231d"),
    "store" : ObjectId("593e7589a489ce07c899210d"),
    "itemcredits" : [ 
        {
            "expireDate" : "10/2019",
            "unitePrice" : "50",
            "itemCredit" : "5"
        }, 
        {
            "expireDate" : "12/2018",
            "unitePrice" : "50",
           "itemCredit" : "3"
        }
    ]
}

我想查询获取匹配相同商店和商品的同一文档的itemcredits.itemCredit的总和，以获得此示例的结果= 8

Answer 1

尝试这样的事情

db.collectionName.aggregate([{$group: {
    '_id': '$_id', 
    "total": {$sum: "$itemcredits.itemcredits" }
}}]);

itemcredits需要是整数