MongoDB查询数组串联？
要进行串联，请在MongoDB中使用$concatArrays。首先让我们创建一个包含文档的集合-
>db.demo14.insertOne({"ListOfStudent":["Carol","Mike","Sam"],"ListOfTeacher":["Robert","David"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e0f754bd7df943a7cec4faa")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.demo14.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5e0f754bd7df943a7cec4faa"),
"ListOfStudent" : [
"Carol",
"Mike",
"Sam"
],
"ListOfTeacher" : [
"Robert",
"David"
]
}以下是连接数组的查询-
> db.demo14.aggregate([
... { "$project": {
... "ListOfPeople": { "$concatArrays": [ "$ListOfStudent", "$ListOfTeacher" ] }
... }}
... ]);这将产生以下输出-
{ "_id" : ObjectId("5e0f754bd7df943a7cec4faa"), "ListOfPeople" : [ "Carol", "Mike", "Sam", "Robert", "David" ] }