MongoDB查询以选择10个最新文档而不更改顺序？
skip()。在下skip()，设置“count()–10”以获取10个最新文档。让我们创建一个包含文档的集合-> db.demo500.insertOne({value:10});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749c5987b6e0e9d18f55a")
}
> db.demo500.insertOne({value:1200});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749c8987b6e0e9d18f55b")
}
> db.demo500.insertOne({value:19});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749cb987b6e0e9d18f55c")
}
> db.demo500.insertOne({value:28});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749cf987b6e0e9d18f55d")
}
> db.demo500.insertOne({value:50});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749d1987b6e0e9d18f55e")
}
> db.demo500.insertOne({value:70});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749d4987b6e0e9d18f55f")
}
> db.demo500.insertOne({value:100});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749d7987b6e0e9d18f560")
}
> db.demo500.insertOne({value:10});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749d9987b6e0e9d18f561")
}
> db.demo500.insertOne({value:98});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749dc987b6e0e9d18f562")
}
> db.demo500.insertOne({value:80});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8749e0987b6e0e9d18f563")
}
> db.demo500.insertOne({value:75});{
"acknowledged" : true,
"insertedId" : ObjectId("5e874c73987b6e0e9d18f564")
}
> db.demo500.insertOne({value:68});{
"acknowledged" : true,
"insertedId" : ObjectId("5e874c78987b6e0e9d18f565")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo500.find();
这将产生以下输出-
{ "_id" : ObjectId("5e8749c5987b6e0e9d18f55a"), "value" : 10 }
{ "_id" : ObjectId("5e8749c8987b6e0e9d18f55b"), "value" : 1200 }
{ "_id" : ObjectId("5e8749cb987b6e0e9d18f55c"), "value" : 19 }
{ "_id" : ObjectId("5e8749cf987b6e0e9d18f55d"), "value" : 28 }
{ "_id" : ObjectId("5e8749d1987b6e0e9d18f55e"), "value" : 50 }
{ "_id" : ObjectId("5e8749d4987b6e0e9d18f55f"), "value" : 70 }
{ "_id" : ObjectId("5e8749d7987b6e0e9d18f560"), "value" : 100 }
{ "_id" : ObjectId("5e8749d9987b6e0e9d18f561"), "value" : 10 }
{ "_id" : ObjectId("5e8749dc987b6e0e9d18f562"), "value" : 98 }
{ "_id" : ObjectId("5e8749e0987b6e0e9d18f563"), "value" : 80 }
{ "_id" : ObjectId("5e874c73987b6e0e9d18f564"), "value" : 75 }
{ "_id" : ObjectId("5e874c78987b6e0e9d18f565"), "value" : 68 }以下是查询以选择10个最新文档而不更改顺序-
> db.demo500.find().skip(db.demo500.count() - 10);
这将产生以下输出-
{ "_id" : ObjectId("5e8749cb987b6e0e9d18f55c"), "value" : 19 }
{ "_id" : ObjectId("5e8749cf987b6e0e9d18f55d"), "value" : 28 }
{ "_id" : ObjectId("5e8749d1987b6e0e9d18f55e"), "value" : 50 }
{ "_id" : ObjectId("5e8749d4987b6e0e9d18f55f"), "value" : 70 }
{ "_id" : ObjectId("5e8749d7987b6e0e9d18f560"), "value" : 100 }
{ "_id" : ObjectId("5e8749d9987b6e0e9d18f561"), "value" : 10 }
{ "_id" : ObjectId("5e8749dc987b6e0e9d18f562"), "value" : 98 }
{ "_id" : ObjectId("5e8749e0987b6e0e9d18f563"), "value" : 80 }
{ "_id" : ObjectId("5e874c73987b6e0e9d18f564"), "value" : 75 }
{ "_id" : ObjectId("5e874c78987b6e0e9d18f565"), "value" : 68 }