mongodb 更新update
1.$inc用法：{$inc:{field:value}}
作用：对一个数字字段的某个field增加value
> db.test1.update({'name':'wang'},{$inc:{age:1}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "name" : "wang", "age" : 20, "sex" : "M" }
2.$set
用法：{$set:{field:value}}
作用：把文档中某个字段field的值设为value
> db.test1.update({'name':'wang'},{$set:{'sex':'F'}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "name" : "wang", "age" : 20, "sex" : "F" }
3.$unset
用法：{$unset:{field:1}}
作用：删除某个字段field
> db.test1.update({'name':'wang'},{$unset:{'sex':1}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang" }
4.$push
用法：{$push:{field:value}}
作用：把value追加到field里。注：field只能是数组类型，如果field不存在，会自动插入一个数组类型
> db.test1.update({'name':'wang'},{$push:{'sex':'F'}})
> db.test1.update({'name':'wang'},{$push:{'sex':'M'}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang", "sex" : ["F","M" ] }
5.pushAll
用法：{$pushAll:{field:value_array}}
作用：用法同$push一样，只是$pushAll可以一次追加多个值到一个数组字段内。
> db.test1.update({'name':'wang'},{$pushAll:{'sex':['M or F','M and F']}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang", "sex" : ["F","M","M or F","M and F" ] }
> db.test1.update({'name':'wang'},{$push:{'sex':['M or F','M and F']}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang", "sex" : ["F","M","M or F","M and F",["M or F","M and F" ] ] }
6.$addToSet
用法：{$addToSet:{field:value}}
作用：加一个值到数组内，而且只有当这个值在数组中不存在时才增加。
> db.test1.update({'name':'wang'},{$addToSet:{'sex':['M or F','MF']}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang", "sex" : [ "F", "M", "M or F", "M and F", [ "M or F", "M and F" ], [ "M or F", "MF" ] ] }
7.$pop
用法：删除数组内第一个值：{$pop:{field:-1}}、删除数组内最后一个值：{$pop:{field:1}}
作用：用于删除数组内的一个值
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang", "sex" : ["F","M","M or F","M and F" ] }
> db.test1.update({'name':'wang'},{$pop:{'sex':1}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang", "sex" : ["F","M","M or F" ] }
8.$pull
用法：{$pull:{field:_value}}
作用：从数组field内删除一个等于_value的值
> db.test1.update({'name':'wang'},{$pull:{'sex':"F"}})
> db.test1.find({'name':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "name" : "wang", "sex" : ["M","M or F" ] }
10.$rename
用法：{$rename:{old_field_name:new_field_name}}
作用：对字段进行重命名
> db.test1.update({'name':'wang'},{$rename:{'name':'names'}})
> db.test1.find({'name':'wang'})
> db.test1.find({'names':'wang'})
{ "_id" : ObjectId("58662477fb6a734e8f45133f"), "age" : 20, "names" : "wang", "sex" : ["M","M or F" ] }
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