MongoDB哪种查询在数组中多次找到相同的值？
要多次查找相同的值，请在MongoDB中使用$where。让我们创建一个包含文档的集合-
> db.demo188.insertOne(
... {
... "ListOfData":[
... {"Data": 100},
... {"Data": 200},
... {"Data": 100}
... ]
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad1c203d395bdc21346bd")
}
> db.demo188.insertOne(
... {
... "ListOfData":[
... {"Data": 100},
... {"Data": 200},
... {"Data": 300}
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad1c203d395bdc21346be")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo188.find();
这将产生以下输出-
{ "_id" : ObjectId("5e3ad1c203d395bdc21346bd"), "ListOfData" : [ { "Data" : 100 }, { "Data" : 200 }, { "Data" : 100 } ] }
{ "_id" : ObjectId("5e3ad1c203d395bdc21346be"), "ListOfData" : [ { "Data" : 100 }, { "Data" : 200 }, { "Data" : 300 } ] }以下是在数组中多次查找相同值的查询-
> db.demo188.find({
... "$where": function() {
... return this.ListOfData.filter(function(d) {
... return d.Data == 100;
... }).length > 1;
... }
...})这将产生以下输出-
{ "_id" : ObjectId("5e3ad1c203d395bdc21346bd"), "ListOfData" : [ { "Data" : 100 }, { "Data" : 200 }, { "Data" : 100 } ] }