元素匹配返回所有数据，而我只需要选择的数据 [英] Elem match is returning all the data whereas I need only the selected data

问题描述

db.mdb.collection('product_master').find({'project_code':'usha-fos', 'product_details' : {$elemMatch:{'Division':'Electric Fans'}}})
                .limit(1000,function(err,results){
                    if(!err){
                        //console.log("projection succeeded");
                       //console.log("its working");
                       //console.log(results);

                        if(results.length==0){
                            console.log("length is 0")
                        }
                        app.send(req,res,results);//this will send the appropriate data to my controller
                    }
                    else{
                        //console.log("it is throwing an error")
                    }
                })

我的JSON格式数据如下:

And my data in JSON format is as follows:

{ 
    "_id" : ObjectId("57df7f5ab7079b1ab4d8a7dc"), 
    "agency_code" : "v5global", 
    "client_code" : "USHA_FOS", 
    "project_code" : "usha-fos", 
    "product_details" : [
        {
            "Division" : "Anything", 
            "Category" : "Ceiling Fans", 
            "Subcategory1" : "CF - UNIVERSAL - SMART", 
            "Subcategory2" : "STELLA", 
            "SKU" : "1200MM STELLA WH CF", 
            "SKU_Code" : "111048511", 
            "Description" : "", 
            "is_active" : "true"
        }, 
        {
            "Division" : "Electric Fans", 
            "Category" : "Ceiling Fans", 
            "Subcategory1" : "CF - ADMIRE - UNDER LIGHT", 
            "Subcategory2" : "FONTANA", 
            "SKU" : "1280MM FONTANA ORCHID GOLD IVORY CF", 
            "SKU_Code" : "111055447", 
            "Description" : "", 
            "is_active" : "true"
        }, 
        {
            "Division" : "AC&R", 
            "Category" : "Ceiling Fans", 
            "Subcategory1" : "CF - ADMIRE - UNDER LIGHT", 
            "Subcategory2" : "FONTANA", 
            "SKU" : "1250MM FONTANA MAPLE ANTIQUE BRASS CF", 
            "SKU_Code" : "111055448", 
            "Description" : "", 
            "is_active" : "true"
        }, 
        {
            "Division" : "Electric Fans", 
            "Category" : "Ceiling Fans", 
            "Subcategory1" : "CF - ADMIRE - UNDER LIGHT", 
            "Subcategory2" : "FONTANA", 
            "SKU" : "1230MM FONTANA LOTUS BLK CHROME CF", 
            "SKU_Code" : "111056414", 
            "Description" : "", 
            "is_active" : "true"
        }, 
        {
            "Division" : "Home Comfort", 
            "Category" : "Ceiling Fans", 
            "Subcategory1" : "CF - ADMIRE - UNDER LIGHT", 
            "Subcategory2" : "FONTANA", 
            "SKU" : "1230MM FONTANA LOTUS STEEL CF", 
            "SKU_Code" : "111056430", 
            "Description" : "", 
            "is_active" : "true"
        }
]}

/*我想要划分为电风扇的数据，但是无论划分如何，我都将获取所有数据. 请帮我*/ /谢谢./

/* I want the data whose division is electric fans but I am getting all the data irrespective of the division. Please help me out */ /Thanks in advance./

推荐答案

$elemmatch(query) returns all rows in a array when there is atleast one row matching the query criteria.

$ elemMatch(projection) 用作投影时，仅返回所有匹配行的第一行.

$elemMatch(projection) returns only the first row of all the matching rows when used as projection.

您可以使用数组聚合运算符 $ filter .

You can easily get all matching rows by using array aggregation operator $filter.

在这种情况下，将根据传递的crtieria过滤产品详细信息.

In this scenario, product details will be filtered based on the crtieria passed.

aggregate([{
    $match: {
        "project_code": 'usha-fos'
    }
}, {
    $project: {
        "agency_code": 1,
        "client_code": 1,
        "project_code": 1,
        "product_details": {
            "$filter": {
                "input": "$product_details",
                "as": "result",
                cond: {
                    $eq: ["$$result.Division", "Electric Fans"]
                }
            }
        }
    }
}])

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