mongodb实践 2
接上一篇：
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#删除数据
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*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()
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#更新数据
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*mongodb官方建议，如果仅仅是更改某些域，那么使用$modifiers 更加合适~
写道
{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 22 }> db.customers.update({name:"joy"},{$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"},{$inc:{age:1}});
> db.customers.find({name:"joy"});{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 24 }{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "name" : "joy", "age" : 23 }{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "name" : "joy", "age" : 23 }?很遗憾只改变了第一条数据:(
update的语法为：db.customers.update(query, object[, upsert_bool, multi_bool])
?，有两个可选参数，我们没有用到，官网上对这几个参数的解释是@
写道
> db.customers.find({name:"joy"});{ "_id" : ObjectId("4ee98be10b240000000027f3"), "name" : "joy", "age" : 25 }{ "_id" : ObjectId("4ee99ce18b12000000004f86"), "name" : "joy", "age" : 24 }{ "_id" : ObjectId("4ee99d0f8b12000000004f87"), "name" : "joy", "age" : 24 }?所有名字叫joy的客户的年龄都增大了一岁。
现在把25岁的joy改成24岁，可以这么来@
> db.customers.update({name:"joy",age:25},{$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：$相当有用，官网的解释是@
写道
{"title" : "mongodb learning","author" : "someone","comments" : [{"by" : "joy","votes" : 1},{"by" : "tim","votes" : 3}]}> db.archives.insert(archive);> db.archives.find();{ "_id" : ObjectId("4ee9ad938b12000000004f88"), "title" : "mongodb learning", "author" : "someone", "comments" : [ { "by" : "joy", "votes" : 1 }, { "by" : "tim", "votes" : 3 } ] }?将joy的评论votes加1@
> db.archives.update({'comments.by':"joy"},{$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:)