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查询解释mongodb入门-8 查询3

2013-05-20 19:48 537 查看
发一下牢骚和主题无关：

继续学下mongodb的查询

$or $nor

$or或者的意思 只要有一个符合就查出了. $nor与$or相反,只要是$or可以查出来的$nor作为去除的部份.

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b8"), "name" : "user6", "age" : 6 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b9"), "name" : "user7", "age" : 7 }
{ "_id" : ObjectId("5198c286c686eb50e2c843ba"), "name" : "user8", "age" : 8 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bb"), "name" : "user9", "age" : 9 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bc"), "name" : "user10", "age" : 10 }
{ "_id" : ObjectId("5198c3cac686eb50e2c843bd"), "name" : "user0", "age" : 20 }
> db.user.find({$or:[{name:"user1"},{age:20}]}) -->这里可以看到$or和其它的$开头方法不同,其它一般都是作为一个键的值,这个是之间作为键的,可能这里解释的不是很清晰,大家理解了就好
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c3cac686eb50e2c843bd"), "name" : "user0", "age" : 20 }

同样$nor就是查询出其它的部份:

> db.user.find({$nor:[{name:"user1"},{age:20}]})
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b8"), "name" : "user6", "age" : 6 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b9"), "name" : "user7", "age" : 7 }
{ "_id" : ObjectId("5198c286c686eb50e2c843ba"), "name" : "user8", "age" : 8 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bb"), "name" : "user9", "age" : 9 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bc"), "name" : "user10", "age" : 10 }


$size 查询数组的长度等于给定数组长度的文档

> db.phone.find()
{ "_id" : ObjectId("5198e20220c9b0dc40419385"), "num" : [ 1, 2, 3 ] }
{ "_id" : ObjectId("5198e21820c9b0dc40419386"), "num" : [ 4, 2, 3 ] }
{ "_id" : ObjectId("5198e22120c9b0dc40419387"), "num" : [ 1, 2, 5 ] }
{ "_id" : ObjectId("5198e51a20c9b0dc40419388"), "state" : 1 }
{ "_id" : ObjectId("519969952b76790566165de2"), "num" : [ 2, 3 ] }
> db.phone.find({num:{$size:4}}) -->num数组长度为4的结果没有
> db.phone.find({num:{$size:3}}) -->长度为3的有三个
{ "_id" : ObjectId("5198e20220c9b0dc40419385"), "num" : [ 1, 2, 3 ] }
{ "_id" : ObjectId("5198e21820c9b0dc40419386"), "num" : [ 4, 2, 3 ] }
{ "_id" : ObjectId("5198e22120c9b0dc40419387"), "num" : [ 1, 2, 5 ] }


$where 自定义的查询

$where的值是一个function,我们可以自己写这个function然后去判断哪些值是我们需要的.它会循环扫描集合中的文档,然后执行函数中的判断,只要我们返回true,此文档就会被查出.但是有一点这个方法的性能不是很好,比如下面的查询我能明显感到一些停顿(与上面讲过的方法比较),有兴趣的考研自己试一下.建议只有在其他$方法不能满足查询的时候,在使用$where查询.

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b8"), "name" : "user6", "age" : 6 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b9"), "name" : "user7", "age" : 7 }
{ "_id" : ObjectId("5198c286c686eb50e2c843ba"), "name" : "user8", "age" : 8 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bb"), "name" : "user9", "age" : 9 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bc"), "name" : "user10", "age" : 10 }
{ "_id" : ObjectId("5198c3cac686eb50e2c843bd"), "name" : "user0", "age" : 20 }
> db.user.find({$where:function(){return this.age == 3 || this.age == 4}})
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }


$type 根据数据类型查询

在mongodb中每一种数据类型都有对应的数字,我们在使用$type的时候需要使用这些数字,文档中给出如下的表示

类型编号
双精度1
字符串2
对象3
数组4
二进制数据5
对象 ID7
布尔值8
日期9
空10
正则表达式11
JavaScript13
符号14
JavaScript（带范围）15
32 位整数16
时间戳17
64 位整数18
最小键255
最大键127
一段例子代码:

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b8"), "name" : "user6", "age" : 6 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b9"), "name" : "user7", "age" : 7 }
{ "_id" : ObjectId("5198c286c686eb50e2c843ba"), "name" : "user8", "age" : 8 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bb"), "name" : "user9", "age" : 9 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bc"), "name" : "user10", "age" : 10 }
{ "_id" : ObjectId("5198c3cac686eb50e2c843bd"), "name" : "user0", "age" : 20 }
{ "_id" : ObjectId("51996ef22b76790566165e47"), "name" : 23, "age" : 33 }
> db.user.find({name:{$type:1}}) -->查找name为双精度的文档
{ "_id" : ObjectId("51996ef22b76790566165e47"), "name" : 23, "age" : 33 }

每日一道理

岭上娇艳的鲜花，怎敌她美丽的容颜？山间清澈的小溪，怎比她纯洁的心灵？

在命令行中type的一些值是不起作用的,这可能与命令行环境有关系,如果谁清晰这个,还请给我留言.

正则表达式

mongodb中查询也支持正则,跟javascript中的正则基本一样,但是不建议使用,因为性能不算是很好.

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b8"), "name" : "user6", "age" : 6 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b9"), "name" : "user7", "age" : 7 }
{ "_id" : ObjectId("5198c286c686eb50e2c843ba"), "name" : "user8", "age" : 8 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bb"), "name" : "user9", "age" : 9 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bc"), "name" : "user10", "age" : 10 }
{ "_id" : ObjectId("5198c3cac686eb50e2c843bd"), "name" : "user0", "age" : 20 }
{ "_id" : ObjectId("51996ef22b76790566165e47"), "name" : 23, "age" : 33 }
> db.user.find({name:/user*/i}) -->查询name以user开头不区分大小写的文档
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b8"), "name" : "user6", "age" : 6 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b9"), "name" : "user7", "age" : 7 }
{ "_id" : ObjectId("5198c286c686eb50e2c843ba"), "name" : "user8", "age" : 8 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bb"), "name" : "user9", "age" : 9 }
{ "_id" : ObjectId("5198c286c686eb50e2c843bc"), "name" : "user10", "age" : 10 }
{ "_id" : ObjectId("5198c3cac686eb50e2c843bd"), "name" : "user0", "age" : 20 }


排序

在mongodb中排序很简单,使用sort方法,传递给它你想按照哪个字段的哪种方式排序即可.这里1代表升序,-1代表降序.

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
> db.user.find().sort({age:1})
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
> db.user.find().sort({age:-1})
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 5 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 4 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 3 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }


group 分组查询

mongodb中的group可以实现类似关系型数据库中的分组的功能,但是mongodb中的group远比关系型数据库中的group强大,可以实现map-reduce功能,至于map-reduce读者自己百度吧,现在比较火.

group中的json参数类似这样{key:{字段:1},initial:{变量:初始值},$reduce:function(doc,prev){函数代码}}.

其中的字段代表,需要按哪个字段分组.变量表示这一个分组中会使用的变量,并且给一个初始值.可以在后面的$reduce函数中使用.$reduce的两个参数,分别代表当前的文档和上个文档执行完函数后的结果.如下我们按年龄分组,同级不同年龄的用户的多少:

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 2 }
> db.user.group({key:{age:1},initial:{count:0},$reduce:function(doc,prev){prev.count++}})
[
{
"age" : 0,
"count" : 1
},
{
"age" : 1,
"count" : 3
},
{
"age" : 2,
"count" : 2
}
]

group更加详细的介绍请看

http://hi.baidu.com/xiyi2008/item/a91d88b90948c4d084dd79a4

这篇文章

distinct

去除查询结果中的重复数据,对原有数据不会产生影响,返回的结果是一个数组.

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 2 }
> db.user.distinct("age")
[ 0, 1, 2 ]


分页查询

在mongodb中实现分页比较简单,需要使用到skip 和limit方法.skip表示跳过前面的几个文档,limit表示显示几个文档.

> db.user.find()
{ "_id" : ObjectId("5198c286c686eb50e2c843b2"), "name" : "user0", "age" : 0 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b3"), "name" : "user1", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b7"), "name" : "user5", "age" : 2 }
> db.user.find().skip(2).limit(3) -->跳过前两个文档查询后面的三个文档,经过测试这两个方法的使用顺序没有影响
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 1 }
> db.user.find().limit(3).skip(2)
{ "_id" : ObjectId("5198c286c686eb50e2c843b4"), "name" : "user2", "age" : 2 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b5"), "name" : "user3", "age" : 1 }
{ "_id" : ObjectId("5198c286c686eb50e2c843b6"), "name" : "user4", "age" : 1 }

暂时是先这样吧.

文章结束给大家分享下程序员的一些笑话语录：

马云喜欢把自己包装成教主，张朝阳喜欢把自己包装成明星，李彦宏喜欢把自己包装成的很知性，丁磊喜欢把自己包装的有创意，李开复总摆出一副叫兽的样子。看来的。其实我想说，缺啥补啥，人之常情。
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