是否有可能在MongoDB中实现切片链？
是的，您可以使用聚合框架来实现。首先让我们创建一个包含文档的集合-
> db.sliceOfSliceDemo.insertOne(
... {
... "Name": "John",
... "Details": [["First 1:1", "First 1:2"],["second 2:1","Second 2:2"]]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ccf3fcfdceb9a92e6aa195a")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.sliceOfSliceDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5ccf3fcfdceb9a92e6aa195a"),
"Name" : "John",
"Details" : [
[
"First 1:1",
"First 1:2"
],
[
"second 2:1",
"Second 2:2"
]
]
}以下是获取切片的查询，即在MongoDB中实现切片链-
> db.sliceOfSliceDemo.aggregate([ {$match:{"Name":"John"}},
{$unwind:"$Details"},
{$unwind:"$Details"},
{$group:{"_id":"$Name","Details":{$last:"$Details"}}},
{$project:{"Name":"$_id","Details":1}} ]);这将产生以下输出-
{ "_id" : "John", "Details" : "Second 2:2", "Name" : "John" }热门推荐
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