MongoDB查询集合中的文档
MongoDB查询集合中的文档参考资料：http://blog.csdn.net/qq_36040184/article/details/54355085
测试：
集合中插入数据
> db.chenji.insert({"name":"张三","年纪":"三年级","年龄":"14"})
WriteResult({ "nInserted" : 1 })
> db.chenji.insert({"name":"王三","年纪":"四年级","年龄":"16"})
WriteResult({ "nInserted" : 1 })
> db.chenji.insert({"name":"王七","年纪":"一年级","年龄":"8"})
WriteResult({ "nInserted" : 1 })
> db.chenji.insert({"name":"张巴","年纪":"一年级","年龄":"9"})
WriteResult({ "nInserted" : 1 })
> db.chenji.insert({"name":"谢娜","年纪":"七年级","年龄":"16"})
WriteResult({ "nInserted" : 1 })
> db.chenji.find()
{ "_id" : ObjectId("59990ec402730a37fe1ee79e"),"name" : "建伟", "年纪" : "二年级","年龄" : "12" }
{ "_id" :ObjectId("59987eee7cd6cda607043cd1"), "name" : "李旭","年纪" : "三年级", "年龄" : "13" }
{ "_id" :ObjectId("5998860a7cd6cda607043cd2"), "name" : "张三","年纪" : "三年级", "年龄" : "14" }
{ "_id" : ObjectId("599886227cd6cda607043cd3"),"name" : "王三", "年纪" : "四年级","年龄" : "16" }
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
{ "_id" :ObjectId("5998866e7cd6cda607043cd6"), "name" : "谢娜","年纪" : "七年级", "年龄" : "16" }
3.1使用条件表达式(=,!=)
//大于： field > value
db.collection.find({field:{$gt:value}});
db.chenji.find({"年龄":{$gt:"6"}});
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
//小于： field < value
db.collection.find({field:{$lt:value}});
> db.chenji.find({"年龄":{$lt:"16"}});
{ "_id" :ObjectId("59990ec402730a37fe1ee79e"), "name" : "建伟","年纪" : "二年级", "年龄" : "12" }
{ "_id" :ObjectId("59987eee7cd6cda607043cd1"), "name" : "李旭","年纪" : "三年级", "年龄" : "13" }
{ "_id" :ObjectId("5998860a7cd6cda607043cd2"), "name" : "张三","年纪" : "三年级", "年龄" : "14" }
//大于等于： field >=value
db.collection.find({field:{$gte:value}});
> db.chenji.find({"年龄":{$gte:"7"}});
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
> db.chenji.find({"年龄":{$gte:"6"}});
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" : ObjectId("599886537cd6cda607043cd5"),"name" : "张巴", "年纪" : "一年级","年龄" : "9" }
//小于等于： fielddb.chenji.find({"年龄":{$lte:"13"}});
{ "_id" : ObjectId("59990ec402730a37fe1ee79e"),"name" : "建伟", "年纪" : "二年级","年龄" : "12" }
{ "_id" :ObjectId("59987eee7cd6cda607043cd1"), "name" : "李旭","年纪" : "三年级", "年龄" : "13" }
//不等于： field != value
db.collection.find({field:{$ne:value}});
db.chenji.find({"name":{$ne:"谢娜"}});
{ "_id" :ObjectId("59990ec402730a37fe1ee79e"), "name" : "建伟","年纪" : "二年级", "年龄" : "12" }
{ "_id" :ObjectId("59987eee7cd6cda607043cd1"), "name" : "李旭","年纪" : "三年级", "年龄" : "13" }
{ "_id" :ObjectId("5998860a7cd6cda607043cd2"), "name" : "张三","年纪" : "三年级", "年龄" : "14" }
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
db.chenji.find({"年纪":{$ne:"三年级"}});
{ "_id" :ObjectId("59990ec402730a37fe1ee79e"), "name" : "建伟","年纪" : "二年级", "年龄" : "12" }
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
{ "_id" :ObjectId("5998866e7cd6cda607043cd6"), "name" : "谢娜","年纪" : "七年级", "年龄" : "16" }
3.2统计(count)、排序(sort)、分页(skip、limit)
> db.chenji.count();
7
> db.chenji.find().count();
7
> db.chenji.find({"年龄":{$lt:"16"}})
{ "_id" :ObjectId("59990ec402730a37fe1ee79e"), "name" : "建伟","年纪" : "二年级", "年龄" : "12" }
{ "_id" :ObjectId("59987eee7cd6cda607043cd1"), "name" : "李旭","年纪" : "三年级", "年龄" : "13" }
{ "_id" :ObjectId("5998860a7cd6cda607043cd2"), "name" : "张三","年纪" : "三年级", "年龄" : "14" }
>
> db.chenji.find({"年龄":{$lt:"16"}}).count();
3
> db.chenji.find({"年纪":{$ne:"三年级"}});
{ "_id" :ObjectId("59990ec402730a37fe1ee79e"), "name" : "建伟","年纪" : "二年级", "年龄" : "12" }
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
{ "_id" :ObjectId("5998866e7cd6cda607043cd6"), "name" : "谢娜","年纪" : "七年级", "年龄" : "16" }
> db.chenji.find({"年纪":{$ne:"三年级"}}).count();
5
排序：默认是按照自身的id号来排序
> db.chenji.find().sort({"年龄":1});
{ "_id" :ObjectId("59990ec402730a37fe1ee79e"), "name" : "建伟","年纪" : "二年级", "年龄" : "12" }
{ "_id" :ObjectId("59987eee7cd6cda607043cd1"), "name" : "李旭","年纪" : "三年级", "年龄" : "13" }
{ "_id" :ObjectId("5998860a7cd6cda607043cd2"), "name" : "张三","年纪" : "三年级", "年龄" : "14" }
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
{ "_id" : ObjectId("5998866e7cd6cda607043cd6"),"name" : "谢娜", "年纪" : "七年级","年龄" : "16" }
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
忽略前两个id的记录，查看接着的三条记录
> db.chenji.find().skip(2).limit(3);
{ "_id" :ObjectId("5998860a7cd6cda607043cd2"), "name" : "张三","年纪" : "三年级", "年龄" : "14" }
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
> db.chenji.find().skip(2).limit(2);
{ "_id" :ObjectId("5998860a7cd6cda607043cd2"), "name" : "张三","年纪" : "三年级", "年龄" : "14" }
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
按年龄倒序排序，并且查看第一行记录
> db.chenji.find().sort({"年龄":-1}).limit(1)
{ "_id" :ObjectId("599886537cd6cda607043cd5"), "name" : "张巴","年纪" : "一年级", "年龄" : "9" }
按年龄倒序排序，并且查看第二行记录
> db.chenji.find().sort({"年龄":-1}).limit(2)
{ "_id" : ObjectId("599886537cd6cda607043cd5"),"name" : "张巴", "年纪" : "一年级","年龄" : "9" }
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
> db.chenji.find().sort({"年龄":-1}).skip(2).limit(2).count(1)
2
> db.chenji.find().sort({"年龄":-1}).skip(1).limit(3)
{ "_id" :ObjectId("599886357cd6cda607043cd4"), "name" : "王七","年纪" : "一年级", "年龄" : "8" }
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
{ "_id" :ObjectId("5998866e7cd6cda607043cd6"), "name" : "谢娜","年纪" : "七年级", "年龄" : "16" }
3.3$or，相当于关系型数据库中的OR，表示或者的关系
查询name为张三或者年龄为16
> db.chenji.find({$or:[{name:"王三"},{"年龄":16}]})
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
> db.chenji.find({$or:[{name:"王三"},{"年龄":12}]})
{ "_id" :ObjectId("599886227cd6cda607043cd3"), "name" : "王三","年纪" : "四年级", "年龄" : "16" }
3.4$nor，表示根据条件过滤掉某些数据
查询name不是张三或者年龄不是13
>db.chenji.find({$nor:[{name:"李旭"},{"年龄":13}]})
3.5$exists，用于查询集合中存在某个键的文档或不存在某个键的文档
查询customer集合中存在name键的所有文档
$exists:1表示真，指存在
$exists:0表示假，指不存在
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