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mongodb实践 2

来源: shenbai 分享至:

接上一篇:

#删除数据

*删除某条数据@

> db.things.remove({i:1});

		> db.things.find({i:1});
		> db.things.find({i:2});
		{ "_id" : ObjectId("4ee8510a0c16000000006ec7"), "i" : 2, "i2" : 4 }
		{ "_id" : ObjectId("4ee8514d0c16000000006edb"), "i" : 2, "i2" : 4, "i3" : 8 }

db.things.remove()会删除things聚集中的所有数据。

甚至可以删除聚集本身@

db.things.drop()

#更新数据

*mongodb官方建议,如果仅仅是更改某些域,那么使用$modifiers 更加合适~

写道

a modifier update has the advantages of avoiding the latency involved in querying and returning the object.
The modifier update also features operation atomicity and very little network data transfer.

*modifiers有如下操作@

写道

$inc 自增/自减
$set 赋值
$unset 删除某个列
$push 追加到原有值后
$pushAll 追加数组到原有值后
$addToSet and $each 向数组添加一个元素/向数组添加多个元素
$pop 移除某个数组元素(-1表示第一个、1表示最后一个)
$pull 移除指定的数组元素
$pullAll 移除多个指定的数组元素
$rename 更新域名
$bit 按位操作,仅限整型

*将客户joy的年龄+1@

> db.customers.find({name:"joy"});

		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 22 }
		> db.customers.update({name:"joy"},{$inc:{age:1}});
		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 23 }

再添加两条数据@

db.customers.save({name:"joy",age:23});db.customers.save({name:"joy",age:23});

如何将所有joy的年龄都变为24呢?

试一下前面的方法@

> db.customers.update({name:"joy"},{$inc:{age:1}});

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 24 }
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "name" : "joy", "age" : 23 }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "name" : "joy", "age" : 23 }

很遗憾只改变了第一条数据:(

update的语法为:db.customers.update(query, object[, upsert_bool, multi_bool])

,有两个可选参数,我们没有用到,官网上对这几个参数的解释是@

写道

query 查询哪些记录需要被更新
object 需要更新的域
upsert 如果为true则有记录时更新记录,没有记录时添加一条新记录(默认值似乎是true)
multi 决定到底是更新所有查询到的记录还是只更新一条(默认值似乎是false)

再试一下@

> db.customers.update({name:"joy"},{$inc:{age:1}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 25 }
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "name" : "joy", "age" : 24 }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "name" : "joy", "age" : 24 }

所有名字叫joy的客户的年龄都增大了一岁。

现在把25岁的joy改成24岁,可以这么来@

> db.customers.update({name:"joy",age:25},{$set:{age:24}});

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 24 }
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "name" : "joy", "age" : 24 }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "name" : "joy", "age" : 24 }

这样在customers中就有三个名字和年龄都相同的客户了:)

添加一个性别域@

> db.customers.update({name:"joy",age:24},{$set:{gender:"m"}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 24, "gender" : "m", "name" : "joy" }
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 24, "gender" : "m", "name" : "joy" }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "gender" : "m", "name" : "joy" }

删除该域@

> db.customers.update({name:"joy",age:24},{$unset:{gender:"m"}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 24, "name" : "joy" }
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 24, "name" : "joy" }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy" }

经过一些步骤,现在数据库中3个joy的年龄不同了,接下来给他们加一个数组域,记录他们的订单记录@

> db.customers.update({name:"joy"},{$push:{orders:"1000"}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 22, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 23, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy", "orders" : [ "1000" ] }

再试试$pushAll@

> db.customers.update({name:"joy",age:22},{$pushAll:{orders:["1001","1002"]}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 22, "name" : "joy", "orders" : [ "1000", "1001", "1002" ] }
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 23, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy", "orders" : [ "1000" ] }

试试$addToSet and $each@

> db.customers.update({name:"joy",age:22},{$addToSet:{orders:{$each:["1003","1004"]}}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 23, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 22, "name" : "joy", "orders" : [ "1000", "1001", "1002", "1003", "1004" ] }

$pop把数组元素弹出@

> db.customers.update({name:"joy",age:22},{$pop:{orders:1}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 23, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 22, "name" : "joy", "orders" : [ "1000", "1001", "1002", "1003" ] }
		> db.customers.update({name:"joy",age:22},{$pop:{orders:-1}},true,true);
		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 23, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 22, "name" : "joy", "orders" : [ "1001", "1002", "1003" ] }

$push也可以把数组元素弹出@

> db.customers.update({name:"joy",age:22},{$pull:{orders:"1002"}},true,true);

		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 23, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 22, "name" : "joy", "orders" : [ "1001", "1003" ] }
		> db.customers.update({name:"joy",age:22},{$pullAll:{orders:["1001","1003"]}},true,true);
		> db.customers.find({name:"joy"});
		{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "age" : 23, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "age" : 24, "name" : "joy", "orders" : [ "1000" ] }
		{ "_id" : ObjectId("4ee98be10b240000000027f3"), "age" : 22, "name" : "joy", "orders" : [ ] }

把orders修改为customer_orders@

> db.customers.update({name:"joy"},{$rename:{orders:"customer_orders"}},true,true);

		Invalid modifier specified $rename

很遗憾:(查了资料才发现$rename这个命令在Version 1.7.2+ 以后才有,而$bit这个命令Version 1.7.5+之后才有。我的测试版本@

> db.version();

		1.6.5

*最后一点,关于$的用法:$相当有用,官网的解释是@

写道

The $ operator (by itself) means "position of the matched array item in the query". Use this to find an array member and then manipulate it.

$指的就是在一次查询中匹配的数组项的位置,通过使用$可以找到数组元素并操作它。(翻译的不好,满头大汗:|)

定义一个文章+评论的数据模式@

> archive = {title:"mongodb learning",author:"someone",comments:[{by:"joy",votes:1},{by:"tim",votes:3}]}

		{
			"title" : "mongodb learning",
			"author" : "someone",
			"comments" : [
				{
					"by" : "joy",
					"votes" : 1
				},
				{
					"by" : "tim",
					"votes" : 3
				}
			]
		}
		> db.archives.insert(archive);
		> db.archives.find();
		{ "_id" : ObjectId("4ee9ad938b12000000004f88"), "title" : "mongodb learning", "author" : "someone", "comments" : [ { "by" : "joy", "votes" : 1 }, { "by" : "tim", "votes" : 3 } ] }

将joy的评论votes加1@

> db.archives.update({'comments.by':"joy"},{$inc:{'comments.$.votes':1}},false,true);

		> db.archives.find({author:"someone"});
		{ "_id" : ObjectId("4ee9ad938b12000000004f88"), "title" : "mongodb learning", "author" : "someone", "comments" : [ { "by" : "joy", "votes" : 2 }, { "by" : "tim", "votes" : 3 } ] }

先到这里,接下来学学Index:)

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