标签：field ros user limit str 第一条 nbsp 集合 name
MongoDB limit 选取 skip跳过 sort排序
在mysql里有order by MongoDB用sort代替order by
> db.user.find() { "_id" : ObjectId("5ca7a4b0219efd687462f965"), "id" : 1, "name" : "jack", "age" : 73 } { "_id" : ObjectId("5ca7a4b7219efd687462f966"), "id" : 2, "name" : "mike", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a4c4219efd687462f967"), "id" : 3, "name" : "peter", "age" : 21 } { "_id" : ObjectId("5ca7a4c4219efd687462f968"), "id" : 4, "name" : "xiaogang", "age" : 34, "hobby" : [ "羽毛球", "篮球", "足球" ] } { "_id" : ObjectId("5ca7a4c4219efd687462f969"), "id" : 5, "name" : "ben", "age" : 24 } { "_id" : ObjectId("5ca7a505219efd687462f96a"), "id" : 6, "name" : "Mary", "age" : 84, "gender" : "男" }
我要从这些 Document 中取出多少个
选取2条Document
> db.user.find().limit(2) { "_id" : ObjectId("5ca7a4b0219efd687462f965"), "id" : 1, "name" : "jack", "age" : 73 } { "_id" : ObjectId("5ca7a4b7219efd687462f966"), "id" : 2, "name" : "mike", "age" : 84, "gender" : "男" }
从整个collection集合的第一条数据Document开始选取两条
我要跳过多少个Document
我要跳过前两个 Document 直接从第三个Document 开始
> db.user.find().skip(2) { "_id" : ObjectId("5ca7a4c4219efd687462f967"), "id" : 3, "name" : "peter", "age" : 21 } { "_id" : ObjectId("5ca7a4c4219efd687462f968"), "id" : 4, "name" : "xiaogang", "age" : 34, "hobby" : [ "羽毛球", "篮球", "足球" ] } { "_id" : ObjectId("5ca7a4c4219efd687462f969"), "id" : 5, "name" : "ben", "age" : 24 } { "_id" : ObjectId("5ca7a505219efd687462f96a"), "id" : 6, "name" : "Mary", "age" : 84, "gender" : "男" }
skip(2) 就是跳过两条Document，从整个collection集合第一条数据Document开始跳过
我只想要第二条和第三条
> db.user.find() { "_id" : ObjectId("5ca7a4b0219efd687462f965"), "id" : 1, "name" : "jack", "age" : 73 } { "_id" : ObjectId("5ca7a4b7219efd687462f966"), "id" : 2, "name" : "mike", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a4c4219efd687462f967"), "id" : 3, "name" : "peter", "age" : 21 } { "_id" : ObjectId("5ca7a4c4219efd687462f968"), "id" : 4, "name" : "xiaogang", "age" : 34, "hobby" : [ "羽毛球", "篮球", "足球" ] } { "_id" : ObjectId("5ca7a4c4219efd687462f969"), "id" : 5, "name" : "ben", "age" : 24 } { "_id" : ObjectId("5ca7a505219efd687462f96a"), "id" : 6, "name" : "Mary", "age" : 84, "gender" : "男" } > > db.user.find().skip(1).limit(2) { "_id" : ObjectId("5ca7a4b7219efd687462f966"), "id" : 2, "name" : "mike", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a4c4219efd687462f967"), "id" : 3, "name" : "peter", "age" : 21 }
跳过第一条数据，从第二条数据开始选取2条数据Document
反过来顺序是一样的
> db.user.find().limit(2).skip(1) { "_id" : ObjectId("5ca7a4b7219efd687462f966"), "id" : 2, "name" : "mike", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a4c4219efd687462f967"), "id" : 3, "name" : "peter", "age" : 21 }
选取两条数据，但要跳过第一条数据，从第二条数据开始选取
sort写法 {} 里面根据什么Field进行排序
1 为升序 , -1 为降序
db.user.find().sort({ sortField:-1 })
将find出来的Document 按照 age 进行 升序 | 降序 排列
升序
> db.user.find().sort({"age":1}) { "_id" : ObjectId("5ca7a4c4219efd687462f967"), "id" : 3, "name" : "peter", "age" : 21 } { "_id" : ObjectId("5ca7a4c4219efd687462f969"), "id" : 5, "name" : "ben", "age" : 24 } { "_id" : ObjectId("5ca7a4c4219efd687462f968"), "id" : 4, "name" : "xiaogang", "age" : 34, "hobby" : [ "羽毛球", "篮球", "足球" ] } { "_id" : ObjectId("5ca7a4b0219efd687462f965"), "id" : 1, "name" : "jack", "age" : 73 } { "_id" : ObjectId("5ca7a4b7219efd687462f966"), "id" : 2, "name" : "mike", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a505219efd687462f96a"), "id" : 6, "name" : "Mary", "age" : 84, "gender" : "男" }
降序
> db.user.find().sort({"age":-1}) { "_id" : ObjectId("5ca7a4b7219efd687462f966"), "id" : 2, "name" : "mike", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a505219efd687462f96a"), "id" : 6, "name" : "Mary", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a4b0219efd687462f965"), "id" : 1, "name" : "jack", "age" : 73 } { "_id" : ObjectId("5ca7a4c4219efd687462f968"), "id" : 4, "name" : "xiaogang", "age" : 34, "hobby" : [ "羽毛球", "篮球", "足球" ] } { "_id" : ObjectId("5ca7a4c4219efd687462f969"), "id" : 5, "name" : "ben", "age" : 24 } { "_id" : ObjectId("5ca7a4c4219efd687462f967"), "id" : 3, "name" : "peter", "age" : 21 }
Limit + Skip + Sort 混搭:
选取第二条第三条第四条 并 按照 age 进行 降序排列
> db.user.find().skip(1).limit(3).sort({age:-1}) { "_id" : ObjectId("5ca7a505219efd687462f96a"), "id" : 6, "name" : "Mary", "age" : 84, "gender" : "男" } { "_id" : ObjectId("5ca7a4b0219efd687462f965"), "id" : 1, "name" : "jack", "age" : 73 } { "_id" : ObjectId("5ca7a4c4219efd687462f968"), "id" : 4, "name" : "xiaogang", "age" : 34, "hobby" : [ "羽毛球", "篮球", "足球" ] }
MongoDB limit 选取 skip跳过 sort排序 方法
标签：field ros user limit str 第一条 nbsp 集合 name
原文地址：https://www.cnblogs.com/mingerlcm/p/10698074.html
