MongoDB中使用find来进行查询，返回一个集合中的文档的子集；

返回文档集合blog中的所有文档：

>db.post.find(){"_id":ObjectId("54a530c3ff0df3732bac1681"),"id":2,"name":"joe","age":30,"sex":1,"school":"marry"}{"_id":ObjectId("54a530c3ff0df3732bac1680"),"id":1,"name":"joe","age":30,"comments":["test2","test9","test5"],"sex":1,"school":"marry"}>

返回指定的文档：

>db.post.find({"id":1}){"_id":ObjectId("54a530c3ff0df3732bac1680"),"id":1,"name":"joe","age":30,"comments":["test2","test9","test5"],"sex":1,"school":"marry"}>

返回指定的键值：

>db.post.find({},{"id":1,"age":1}){"_id":ObjectId("54a530c3ff0df3732bac1681"),"id":2,"age":30}{"_id":ObjectId("54a530c3ff0df3732bac1680"),"id":1,"age":30}>

默认总是会返回“_id”键，使用下面的方法可以不返回“ _id”键：

>db.post.find({},{"id":1,"age":1,"_id":0}){"id":2,"age":30}{"id":1,"age":30}>


可以将多个条件组合在一起，例如查询名字为“Joe”且ID为1的文档：

>db.post.find({"name":"joe"}){"_id":ObjectId("54a530c3ff0df3732bac1681"),"id":2,"name":"joe","age":30,"sex":1,"school":"marry"}{"_id":ObjectId("54a530c3ff0df3732bac1680"),"id":1,"name":"joe","age":30,"comments":["test2","test9","test5"],"sex":1,"school":"marry"}>db.post.find({"name":"joe","id":1}){"_id":ObjectId("54a530c3ff0df3732bac1680"),"id":1,"name":"joe","age":30,"comments":["test2","test9","test5"],"sex":1,"school":"marry"}>