如何在mongodb中查詢子文檔？

Question

如何在子文檔中查詢子文檔？

如何在商業文件中檢索城市名稱。

{
    "_id" : " c2 ",
    "commercial" : {
        " type " : " restaurant ",
        " sale_type " : " sale ",
        " owner_name " : " josi schmit",
        " address " : {
            " street " : " kleine rittergasse ",
            " plot_no " : 4,
            " city " : " frankfurt ",
            " state " : " hessen ",
            " country " : "germany ",
            "postal_code " : 60329,
            "email" : " josi123@gmail.com"
        },
        " total_area " : " 300 sq meters ",
        " sale_price(EUR) " : 100000,
        " features " : {
            " lifts " : 1,
            " heating " : true,
            " parking " : true,
            " kitchen " : true,
            " security_cameras " : true,
            " furniture " : true
        }
    }
}

這是我的查詢，但我知道我錯了，請幫助我。

db.property.find（{“ _id”：“ c2”，“ address.city”：“ c2”}）

問候Sreekanth

Answer 1

實際上，有兩種方法可以做到這一點：

1. db.property.find ( { "_id": "c2", "commercial.address.city": "c2" }, {"commercial.address.city": true} )
2. db.property.find ( { "_id": "c2", "commercial": { "address" : { "city": "c2" }}} )

兩種情況的區別在於，在第一種情況下，如果您有一個索引commercial.address.city ，mongo將遵循該index ，第二種則不會，因此我建議您使用第一個