Question

我有一份文件......

doc =  
    { 
        "Loan_Num"       : "Loan002",
        "Info" : "Loan for processing details."
        "Loan_Items" :   [
                            {
                                "Invoice_Num"  : "32134324",
                                "Quantity"  : 1,
                                "Amount_Required" : "£4"
                            },

                            {
                                "Book_Barcode"  : "22222",
                                "Quantity"  : 1,
                                "Amount_Required" : "£2"
                                "Amount_Payed" : true
                            }
                        ]
    };

我试图创建一个查询以带回任何包含＆＃34; Amount_Required＆＃34;关键，但没有＆＃34; Amount_Payed＆＃34;键。

所以从上面的文件中我会期待这个结果......

    { 
        "Loan_Num"       : "Loan002",
        "Info" : "Loan for processing details."
        "Loan_Items" :   [
                            {
                                "Invoice_Num"  : "32134324",
                                "Quantity"  : 1,
                                "Amount_Required" : "£4"
                            }
                        ]
    };

这是我的Java代码......

 BasicDBObject searchQuery = new BasicDBObject();
    searchQuery.append("Loan_Num", "Loan002");
    searchQuery.append("Loan_Items.Fine_Amount", new BasicDBObject("$exists", true));
    searchQuery.append("Loan_Items.Fine_Payed", new BasicDBObject("$exists", false));

问题是它不会返回任何东西，因为＆＃34; Amount_Played＆＃34;存在于数组的第二个元素中。我怎么能实现这个结果？ - 非常感谢

Answer 1

您可以尝试使用$elemMatch：

您的查询将如下所示：

db.collection.find({"Loan_Items" : {$elemMatch : { "Amount_Required" : { $exists : true}, "Amount_Payed" : { $exists : false}}}})

希望这有帮助！

MongoClient如果使用Java匹配，则返回数组中的单个项

1 个答案: