mongodb compass aggregate

Label:in the two previous articles the basic aggregation function of data aggregation in MongoDB count, distinct, group > and the MapReduce of data aggregation in MongoDB >, we've provided two implementations for data aggregation, and today, in this article, we talk about another way to implement data aggregation in MongoDB-the aggregation pipeline

consecutive $skip will be merged into one, followed by a number of two $skip.Two consecutive $match. are merged into 1, the conditions are merged together.{$sort: {Age:-1}},{$skip: 10},{$limit: 5}{$sort: {Age:-1}},{$limit: 15}{$skip: 10}Example{$sort: {Age:-1}},{$skip: 10},{$limit: 5}====>>>>{$sort: {Age:-1}},{$limit: 15}{$skip: 10}====>>>>$sort + $limit Merge{$limit: 100},{$skip: 5},{$limit: 10},{$skip: 2}==========>>>>>>>{$limit: 100},{$limit: 15},{$skip: 5},{$skip: 2}=========>>>>>>>>>{$limi

You need to add translatefields values to the following collection according to Lastupdate by day.Rs_test:secondary>db.new_result.find ();{ "_id" :objectid (" 57fb0756e31f84a56ed41889 ")," Lastupdate ":isodate (" 2016-09-02t01:35:02.471z ")," Translatefields ":9}{" _id ":objectid (" 57fb0756e31f84a56ed4188a ")," Lastupdate ":isodate (" 2016-09-05t11:13:28.344z ")," Translatefields ":10}{" _id ":objectid (" 57fb0756e31f84a56ed4188b ")," Lastupdate ":isodate (" 2016-09-05t09:26:41.016z ")," Transl

Tags: MongoDB aggregate multiple grouping conditionsWhen using aggregate for grouping, multiple grouping conditions are as followsNative sql:Db.test.aggregate ({$group: {_id:{name: ' $name ', Pro: ' $pro},total:{$sum: ' $num '}}},{$project: {Total:1}})In Java, this corresponds to the following:Grouped according to Subjname and province dbobject groupfields = new

go out of the _id field, and then sort by the cat_id,color of the item, and the result skips a row. Take only 30 hang records and push the results into the result set[{$math: {goods_price:{$gte:3000}}}, {$project: {cat_id:1,goods_name:1, Goods_number:1, _id:0}}, {$group: {_id:{cat_id:"$cat _id", Color: "$color"}, total:{$sum: "$goods _number"}}}, {$skip:1}, {$limit:30}, {$out:"Result"} ] . MapReduce Method*Grammatical StructureDb.collection.mapReduce (function() {Emit ( This. cat_

MONGO Aggregate query:Db.collection.aggregate ({$group: {_id: ' $id ',//' $_id ' represents the _id column max_value:{$max in the Reference collection: ' $times '}//' $times ' represents Refer to The Times column in the collection}, $match: {times:{$gte: 100}})Equivalent to SQL query:Select _id, Max (times) from Collectionwhere times>=100This article is from the architect's path blog, so be sure to keep this source http://lizhuquan0769.blog.51cto.com/