在MongoDB中查找当前和以前的文档
要获取当前和以前的文档，请使用sort()。由于我们只需要2个文档，因此请使用LIMIT(2)。
让我们创建一个包含文档的集合-
> db.demo360.insertOne({id:101,"Name":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e56a10c54a481fef8ec7a15")
}
> db.demo360.insertOne({id:102,"Name":"David"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e56a11254a481fef8ec7a16")
}
> db.demo360.insertOne({id:103,"Name":"Bob"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e56a11a54a481fef8ec7a17")
}
> db.demo360.insertOne({id:104,"Name":"Mike"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e56a11f54a481fef8ec7a18")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo360.find();
这将产生以下输出-
{ "_id" : ObjectId("5e56a10c54a481fef8ec7a15"), "id" : 101, "Name" : "Chris" }
{ "_id" : ObjectId("5e56a11254a481fef8ec7a16"), "id" : 102, "Name" : "David" }
{ "_id" : ObjectId("5e56a11a54a481fef8ec7a17"), "id" : 103, "Name" : "Bob" }
{ "_id" : ObjectId("5e56a11f54a481fef8ec7a18"), "id" : 104, "Name" : "Mike" }以下是在MongoDB中查找当前和先前文档的查询-
> db.demo360.find({ id: { $lte: 102 } }, {id:1, Name: 1 }).sort({_id: -1}).limit(2);这将产生以下输出-
{ "_id" : ObjectId("5e56a11254a481fef8ec7a16"), "id" : 102, "Name" : "David" }
{ "_id" : ObjectId("5e56a10c54a481fef8ec7a15"), "id" : 101, "Name" : "Chris" }