通过MongoDB中的聚合框架将嵌入式对象检索为文档？
要将嵌入式对象作为文档检索，请使用聚合$replaceRoot。首先让我们创建一个包含文档的集合-
> db.embeddedObjectDemo.insertOne(
{ _id: new ObjectId(),
"UserDetails": { "UserName": "John", "UserAge": 24, "UserEmailId": "John22@gmail.com" }
}
);
{
"acknowledged" : true,
"insertedId" : ObjectId("5ced580fef71edecf6a1f693")
}
> db.embeddedObjectDemo.insertOne( { _id: new ObjectId(), "UserDetails": { "UserName": "Carol", "UserAge": 26, "UserEmailId": "Carol123@gmail.com" } } );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ced5828ef71edecf6a1f694")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.embeddedObjectDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5ced580fef71edecf6a1f693"),
"UserDetails" : {
"UserName" : "John",
"UserAge" : 24,
"UserEmailId" : "John22@gmail.com"
}
}
{
"_id" : ObjectId("5ced5828ef71edecf6a1f694"),
"UserDetails" : {
"UserName" : "Carol",
"UserAge" : 26,
"UserEmailId" : "Carol123@gmail.com"
}
}以下是通过MongoDB中的聚合框架将嵌入式对象作为文档检索的查询-
> db.embeddedObjectDemo.aggregate( [
{
$replaceRoot: { newRoot: "$UserDetails" }
}
] );这将产生以下输出-
{ "UserName" : "John", "UserAge" : 24, "UserEmailId" : "John22@gmail.com" }
{ "UserName" : "Carol", "UserAge" : 26, "UserEmailId" : "Carol123@gmail.com" }