假设我有多个集合，我想将它们作为一个流来处理。最简单的方法是什么？是否有可以为我执行此操作的实用程序类，还是我必须自己滚动一些东西？如果我的问题不清楚，这基本上就是我想要做的:CollectionusaRegions;CollectioncanadaRegions;CollectionmexicoRegions;StreamnorthAmericanRegions=collect(usaRegions,canadaRegions,mexicoRegions);publicStreamcollect(T...){/*Whatgoeshere?*/} 最佳答案
我尝试聚合操作'$group'..我想获得多组结果。我的数据是这样的..items:[{director:"James",category:"fruit",name:"apple",money:5000},{director:"James",category:"toy",name:"dragon",money:15000},{director:"Sam",category:"fruit",name:"orange",money:3500}]我想得到结果，这个!!directorList:[{director:"James",money:20000},{director:"Sam",mo
在使用组时，我需要很少的值通过管道(无需更改)传递到后续管道聚合器例如，如果我的输入是{"_id":1,"tags":["a","b","b","c"],"text":"a"},{"_id":2,"tags":["a","c"],"text":"b"}我喜欢这样的输出{_id:1,tags:[a,b,c],text:a},{_id:2,tags:[a,c],text:b}我做了一个放松和分组，并执行$addToSet来删除重复项。我的问题是如何制作text按原样出现在输出中。文本键和值只需要通过这个管道，但是我不得不使用累加器到目前为止我试过这段代码usetestvarunwind={
我有收款账户:{"_id":ObjectId("571a0e145d29024733793cfe"),"name":"Cash","user":ObjectId("571a0e145d29024733793cfc")}和交易。事务可以有不同的字段:{"_id":ObjectId("571a0e145d29024733793d06"),"amount":100,"type":"earned","account":ObjectId("571a0e145d29024733793cfe"),"user":ObjectId("571a0e145d29024733793cfc"),},{"_id"
给定一组修改过的记录和一组原始记录。我希望能够编写一个查询，从根本上给出从original“set”到modified“set”的集合差异。所以给定两个集合，原始的和修改的，如下所示:{"_id":1,"set":"original","key":"foo","element":"bar"}{"_id":2,"set":"original","key":"bar","element":"old"}{"_id":3,"set":"original","key":"qux","element":"abc"}#Deleted{"_id":4,"set":"modified","key":"f
我有一个对象存储在我的集合中，如下所示:[{"_id":ObjectId("56bcbe570793be2e5025567e"),"CarPlate":"AB123CD","Brand":"BMW","Version":"316d","Description":"BMW316d","Prices":[{"PriceType":NumberInt(0),"VatType":NumberInt(0),"Currency":"EUR","Value":20100.0},{"PriceType":NumberInt(3),"VatType":NumberInt(0),"Currency":"E
我有一个包含以下示例数据的成员集合{"_id":ObjectId("50f6632d89862009f4c80e0f"),"_Ten":ObjectId("50f6632d89862009f4c80e0e"),"active":true,"role":"Administrator","_t":"User"}{"_id":ObjectId("50fe895678415503d022945f"),"_Ten":ObjectId("50f6632d89862009f4c80e0e"),"active":true,"role":"Contributor","_t":"User"}{"_id":
我正在尝试查询一个集合并检索过去7天(不包括当天)每一天的平均值。在某些或所有的日子里，可能没有平均值。这是我目前所拥有的:vardateTill=moment({hour:0,minute:0}).subtract(1,'days')._dvardateSevenDaysAgo=moment({hour:0,minute:0}).subtract(7,'days')._d;Rating.aggregate([{$match:{userTo:facebookId,timestamp:{$gt:dateSevenDaysAgo,$lt:dateTill}}},{$group:{_id:{
给定以下数据集:{"_id":1,"city":"Yuma","cat":"roads","Q1":0,"Q2":25,"Q3":0,"Q4":0}{"_id":2,"city":"Reno","cat":"roads","Q1":30,"Q2":0,"Q3":0,"Q4":60}{"_id":3,"city":"Yuma","cat":"parks","Q1":0,"Q2":0,"Q3":45,"Q4":0}{"_id":4,"city":"Reno","cat":"parks","Q1":35,"Q2":0,"Q3":0,"Q4":0}{"_id":5,"city":"Yuma",
我有一个MongoDB文档集合，该集合具有两个属性:类型和值。[{type:"A",value:"1"},{type:"A",value:"2"},{type:"B",value:"1"},{type:"B",value:"2"},{type:"C",value:"1"},{type:"C",value:"2"}]如何在不涉及任何JavaScript的情况下使用单个查询获取每种类型的随机文档？我试图使用聚合框架找出一些东西db.collection.aggregate([{$group:{_id:"$type",item:{$push:"$$ROOT"}}},{$sample:{siz
