在MongoDB文档中获取数组项？
要在MongoDB文档中获取数组项，请使用点（。）表示法。让我们创建一个包含文档的集合-
> db.demo29.insertOne({"StudentDetails":[{"StudentName":"Chris","StudentMarks":58},{"StudentName":"Bob","StudentMarks":69}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e15fcc08f2315c2efc48e6e")
}
>db.demo29.insertOne({"StudentDetails":[{"StudentName":"David","StudentMarks":97},{"StudentName":"Carol","StudentMarks":96}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e15fcd38f2315c2efc48e6f")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo29.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5e15fcc08f2315c2efc48e6e"),
"StudentDetails" : [
{
"StudentName" : "Chris",
"StudentMarks" : 58
},
{
"StudentName" : "Bob",
"StudentMarks" : 69
}
]
}
{
"_id" : ObjectId("5e15fcd38f2315c2efc48e6f"),
"StudentDetails" : [
{
"StudentName" : "David",
"StudentMarks" : 97
},
{
"StudentName" : "Carol",
"StudentMarks" : 96
}
]
}以下是在MongoDB文档中获取数组项的查询-
> db.demo29.find({"StudentDetails.StudentName":"David"});这将产生以下输出-
{ "_id" : ObjectId("5e15fcd38f2315c2efc48e6f"), "StudentDetails" : [ { "StudentName" : "David", "StudentMarks" : 97 }, { "StudentName" : "Carol", "StudentMarks" : 96 } ] }