如何在猫鼬中找到最新的子文档
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【中文标题】如何在猫鼬中找到最新的子文档【英文标题】：How to find most recent subdocument in mongoose 【发布时间】：2016-06-19 01:35:51 【问题描述】：我有名为RegisterList 的猫鼬文档，该文档包含名为Booking 的子文档。
这里我需要检索子文档，也就是最近添加的子文档
下面是我的 json 数据
[
_id: "56a3174bfc518cd014af7abd",
area_name: "padi",
name: "Vignesh",
email: "vignesh4008@gmail.com",
mobile_no: "9282438685",
otp: "1625",
__v: 0,
date: "2016-01-23T06:01:47.450Z",
booking: [
name: "Vignesh",
mobile: "9282438685",
can_name: "Kinley",
can_quantity: "2",
can_cost: "80",
can_path: "http://test15.watervan.in/wp-content/uploads/2015/07/p-95-WV-Kinley-25l.png",
delivery_date: "23-01-2016",
delivery_timeslot: "3pm-8pm",
order_id: "S16064",
subscription: "true",
subscription_type: "EveryDay",
total_cost: "560",
address: "12,Ramanrajan street,,padi,Chennai",
_id: "56a3174bfc518cd014af7abe",
delivered_at: "2016-01-22T18:30:00.000Z",
ordered_at: "2016-01-23T06:01:47.451Z",
status: "Delivered"
,
name: "Vignesh",
mobile: "9282438685",
can_name: "Kinley",
can_quantity: "2",
can_cost: "80",
can_path: "http://test15.watervan.in/wp-content/uploads/2015/07/p-95-WV-Kinley-25l.png",
delivery_date: "24-01-2016",
delivery_timeslot: "3pm-8pm",
address: "12,Ramanrajan street,,padi,Chennai",
order_id: "S16064",
subscription_type: "EveryDay",
_id: "56a31ba2d55894ec15eac1cf",
ordered_at: "2016-01-23T06:20:18.479Z",
status: "UnderProcess"
]
,
_id: "56a0bc8d3306f388131e56c6",
area_name: "kodambakkam",
name: "Ganesh",
email: "ganesh@gmail.com",
mobile_no: "9042391491",
otp: "7828",
__v: 0,
date: "2016-01-21T11:10:05.074Z",
booking: [
name: "Ganesh",
mobile: "9042391491",
can_name: "Bisleri",
can_quantity: "5",
can_cost: "250",
can_path: "http://test15.watervan.in/wp-content/uploads/2015/07/p-95-WV-Kinley-25l.png",
delivery_date: "23-01-2016",
delivery_timeslot: "3pm-8pm",
order_id: "S12348",
subscription: "true",
subscription_type: "Alternate",
total_cost: "1000",
address: "15/A,Main Street,kodambakkam,Chennai",
_id: "56a3164dc2c549e811c0d08f",
delivered_at: "2016-01-22T18:30:00.000Z",
ordered_at: "2016-01-23T05:57:33.169Z",
status: "Delivered"
,
name: "Ganesh",
mobile: "9042391491",
can_name: "Bisleri",
can_quantity: "5",
can_cost: "250",
can_path: "http://test15.watervan.in/wp-content/uploads/2015/07/p-95-WV-Kinley-25l.png",
delivery_date: "25-01-2016",
delivery_timeslot: "3pm-8pm",
address: "15/A,Main Street,kodambakkam,Chennai",
order_id: "S12348",
subscription_type: "Alternate",
_id: "56a31c29d55894ec15eac1d0",
ordered_at: "2016-01-23T06:22:33.307Z",
status: "UnderProcess"
]
]
如何单独找到最近插入的子文档。在给定的 JsonCode 中。
我们将不胜感激...
更新：
我需要为delivery_date 和status 找到AND 条件的数据，那么我该如何编写猫鼬查询来获取数据
【问题讨论】：
不完全清楚你在问什么。您是指集合中每个文档的数组中最新的"ordered_at" 值吗？或者您可能是指集合中 "all" 文档中具有最新值的子文档？无论如何，在任何给定文档中，“最后一个”数组项将始终是最新的，除非您专门在位置添加新项或在更新时对数组进行排序。
完全正确您是指集合中每个文档的数组中最近的“ordered_at”值
如果您通过$push 运算符将子文档推送到booking 数组，它会将元素插入到数组的末尾。除非在$position 之内。
所以我们正在寻找的使操作变得简单的说明是，如果“最新”总是在数组的末尾（默认情况下它会在没有其他修改的情况下）那么所有你真正要求的是要从每个文档返回的数组的“最后一个”元素。当然，有一个内置的“投影”运算符可以做到这一点，而且我也确信之前已经在这里提出过直接问题。
你想要最近的ordered_at，可能是***.com/questions/16497016/…的重复？
【参考方案1】：
基于假设，您可以使用聚合框架获取最新的子文档。
Mongodb 3.2+版本
db.col.aggregate([
$project:
"area_name" : 1,
"name" : 1,
"email" : 1,
"mobile_no" :1,
"otp" : 1,
"__v" : 1,
"date" : 1,
"booking": $slice :["$booking",-1]
])
MongoDB 版本
db.col.aggregate([
// Stage 1
$unwind: "$booking"
,
// Stage 2
$sort:
"booking.ordered_at":-1
,
// Stage 3
$group:
_id:
id: "$_id",
"area_name" : "$area_name",
"name" : "$name",
"email" : "$email",
"mobile_no" :"$mobile_no",
"otp" : "$opt",
"date" : "$date"
,
booking:$first: "$booking"
,
// Stage 4
$project:
_id: 0,
_id: "$_id.id",
"area_name" : "$_id.area_name",
"name" : "$_id.name",
"email" : "$_id.email",
"mobile_no" :"$_id.mobile_no",
"otp" : "$_id.opt",
"date" : "$_id.date",
"booking": 1
]);
根据您提供的示例文档，输出如下所示
"_id" : "56a3174bfc518cd014af7abd",
"booking" :
"name" : "Vignesh",
"mobile" : "9282438685",
"can_name" : "Kinley",
"can_quantity" : "2",
"can_cost" : "80",
"can_path" : "http://test15.watervan.in/wp-content/uploads/2015/07/p-95-WV-Kinley-25l.png",
"delivery_date" : "24-01-2016",
"delivery_timeslot" : "3pm-8pm",
"address" : "12,Ramanrajan street,,padi,Chennai",
"order_id" : "S16064",
"subscription_type" : "EveryDay",
"_id" : "56a31ba2d55894ec15eac1cf",
"ordered_at" : "2016-01-23T06:20:18.479Z",
"status" : "UnderProcess"
,
"area_name" : "padi",
"name" : "Vignesh",
"email" : "vignesh4008@gmail.com",
"mobile_no" : "9282438685",
"date" : "2016-01-23T06:01:47.450Z"
"_id" : "56a0bc8d3306f388131e56c6",
"booking" :
"name" : "Ganesh",
"mobile" : "9042391491",
"can_name" : "Bisleri",
"can_quantity" : "5",
"can_cost" : "250",
"can_path" : "http://test15.watervan.in/wp-content/uploads/2015/07/p-95-WV-Kinley-25l.png",
"delivery_date" : "25-01-2016",
"delivery_timeslot" : "3pm-8pm",
"address" : "15/A,Main Street,kodambakkam,Chennai",
"order_id" : "S12348",
"subscription_type" : "Alternate",
"_id" : "56a31c29d55894ec15eac1d0",
"ordered_at" : "2016-01-23T06:22:33.307Z",
"status" : "UnderProcess"
,
"area_name" : "kodambakkam",
"name" : "Ganesh",
"email" : "ganesh@gmail.com",
"mobile_no" : "9042391491",
"date" : "2016-01-21T11:10:05.074Z"
【讨论】：
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