使用简单查询在MongoDB中过滤文档？
您可以使用$match。$match过滤文档以仅将符合指定条件的文档传递到下一个管道阶段。让我们创建一个包含文档的集合-
> db.demo629.insertOne(
... {
...
... "Subject": [
... "MySQL",
... "MongoDB"
... ],
... "details": [
... {
... Name:"Chris",
... "Marks":78
... },
... { Name:"David",
... "Marks":89
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e9ae9f56c954c74be91e6b9")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo629.find();
这将产生以下输出-
{ "_id" : ObjectId("5e9ae9f56c954c74be91e6b9"), "Subject" : [ "MySQL", "MongoDB" ], "details" : [ { "Name" : "Chris", "Marks" : 78 }, { "Name" : "David", "Marks" : 89 } ] }以下是使用简单查询在MongoDB中过滤文档的查询-
> db.demo629.aggregate([
... {"$unwind": "$details"},
... {"$match": {"details.Name": 'Chris', "Subject": {"$in":["Java","MySQL","Python","C","C++"]}}},
... {"$project": {"details": 1, "_id": 0}}
... ]);这将产生以下输出-
{ "details" : { "Name" : "Chris", "Marks" : 78 } }