mongodb入门-12更新2

mongodb入门-12更新2 mongodb入门-11更新1 http://www.2cto.com/database/201305/213137.html 继续介绍mongoDB中的更新. $inc 为一个字段添加加上一个值,这个方法只能对数字操作,也就是说只能给数字加上一个值,当然这个值可以是负数. [html] db.user.find()

mongodb入门-12更新2

mongodb入门-11更新1

http://www.2cto.com/database/201305/213137.html

继续介绍mongoDB中的更新.

$inc

为一个字段添加加上一个值,这个方法只能对数字操作,也就是说只能给数字加上一个值,当然这个值可以是负数.

[html]

> db.user.find()

{ "_id" : 2, "name" : "user2", "age" : 2 }

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 6 }

> db.user.update({name:"user2"},{$inc:{age:10}}) -->将name为user2的年龄age加上10

> db.user.find()

{ "_id" : 2, "name" : "user2", "age" : 12 }

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 6 }

> db.user.update({name:"user6"},{$inc:{age:-4}}) -->将name为user6的年龄age加上-4,也就是减去4

> db.user.find()

{ "_id" : 2, "name" : "user2", "age" : 12 }

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 2 }

$set

当文档中包含该字段的时候,更新该字段,如果该文档中没有该字段,则为本文档添加一个字段.

[html]

> db.user.find()

{ "_id" : 2, "name" : "user2", "age" : 12 }

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 2 }

> db.user.update({name:"user2"},{$set:{age:20}}) -->将name为user2的age设置为20

> db.user.find()

{ "_id" : 2, "name" : "user2", "age" : 20 }

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 2 }

> db.user.update({name:"user2"},{$set:{sex:"nan"}}) -->将name为user2的sex设置为nan,但是没有该字段,所以为该文档添加sex字段并赋值为nan

> db.user.find()

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 2 }

{ "_id" : 2, "age" : 20, "name" : "user2", "sex" : "nan" }

$unset

删除文档中的一个字段.

[html]

> db.user.find()

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 2 }

{ "_id" : 2, "age" : 20, "name" : "user2", "sex" : "nan" }

> db.user.update({name:"user2"},{$unset:{sex:1}}) -->删除name为user2的sex字段.如果删除一个不存在的字段,并不会报错,没有什么效果

> db.user.find()

{ "_id" : 3, "name" : "user3", "age" : 3 }

{ "_id" : 4, "name" : "user4", "age" : 4 }

{ "_id" : 5, "name" : "user5", "age" : 5 }

{ "_id" : 6, "name" : "user6", "age" : 2 }

{ "_id" : 2, "age" : 20, "name" : "user2" }

$push

将一个数字存入一个数组,分为三种情况,如果该字段存在,则直接将数字存入数组.如果该字段不存在,创建字段并且将数字插入该数组.如果更新的字段不是数组,会报错的.

[html]

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4 ] }

{ "_id" : 2, "text" : "test" }

> db.test.update({_id:1},{$push:{ary:5}}) -->数组存在 直接存入

> db.test.find()

{ "_id" : 2, "text" : "test" }

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5 ] }

> db.test.update({_id:2},{$push:{ary:6}}) -->数组不村子,创建数组并存入

> db.test.find()

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5 ] }

> db.test.update({_id:2},{$push:{text:6}}) -->更新字段存在但不是数组报错

Cannot apply $push/$pushAll modifier to non-array

如果我们想将多个值一起压入我们可能会将一个数组直接存入,但是这样是不对的,$push一次只会存入一个字段,代码如下:

[html]

> db.test.update({_id:1},{$push:{ary:[6,7]}})

> db.test.find()

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ] ] }

实现上面的功能我们可以使用下面的$pushAll

$pushAll

将多个数值一次存入数组.

[html]

> db.test.update({_id:1},{$pushAll:{ary:[8,9]}})

> db.test.find()

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 8, 9 ] }

$addToSet

与$push功能相同讲一个数字存入数组,不同的是如果数组中有这个数字,将不会插入,只会插入新的数据,同样也会有三种情况,与$push相同.

[html]

> db.test.find()

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 8, 9 ] }

> db.test.update({_id:2},{$addToSet:{ary:7}}) -->ary中没有7,插入成功

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 8, 9 ] }

{ "_id" : 2, "ary" : [ 6, 7 ], "text" : "test" }

> db.test.update({_id:2},{$addToSet:{ary:7}}) -->ary中有7,插入失败

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 8, 9 ] }

{ "_id" : 2, "ary" : [ 6, 7 ], "text" : "test" }

其他的两种情况自己去测试.

$pop

删除数组最后一个元素

[html]

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 8, 9 ] }

{ "_id" : 2, "ary" : [ 6, 7 ], "text" : "test" }

> db.test.update({_id:2},{$pop:{ary:1}})

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 8, 9 ] }

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

$pull

删除数组中的一个元素,如果删除的字段不是数组,会报错

[html]

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 8, 9 ] }

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

> db.test.update({_id:1},{$pull:{ary:8}})

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 9 ] }

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

$pullAll

删除数组中的多个值,跟pushAll与push的关系类似.

[html]

> db.test.find()

{ "_id" : 1, "ary" : [ 1, 2, 3, 4, 5, [ 6, 7 ], 9 ] }

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

> db.test.update({_id:1},{$pullAll:{ary:[1,2,8]}})

> db.test.find()

{ "_id" : 1, "ary" : [ 3, 4, 5, [ 6, 7 ], 9 ] }

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

$rename

为字段改名

[html]

> db.test.find()

{ "_id" : 1, "ary" : [ 3, 4, 5, [ 6, 7 ], 9 ] }

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }

> db.test.update({_id:1},{$rename:{ary:"aryNew"}})

> db.test.find()

{ "_id" : 1, "aryNew" : [ 3, 4, 5, [ 6, 7 ], 9 ] }

{ "_id" : 2, "ary" : [ 6 ], "text" : "test" }