MongoDB基础命令杂记
查询年龄大于30的记录： > db.students.find({Age: {$gt: 30}}){ "_id" : ObjectId("587bd99ea954a5d5a876fb26"), "name" : "Ou Yangfeng", "Age" : 90, "Course" : "HaMegong" }
{ "_id" : ObjectId("587bd9f4a954a5d5a876fb28"), "name" : "Guo Jing", "Age" : 40, "Course" : "Xianglong Shibazhang" }
查找年龄20和40的记录：
> db.students.find({Age:{$in: }})
{ "_id" : ObjectId("587bd9bfa954a5d5a876fb27"), "name" : "Yang Guo", "Age" : 20, "Course" : "Meinv Quan" }
{ "_id" : ObjectId("587bd9f4a954a5d5a876fb28"), "name" : "Guo Jing", "Age" : 40, "Course" : "Xianglong Shibazhang" }
查找年龄不是20和40的记录：
> db.students.find({Age:{$nin: }})
$or： 或运算，语法格式{$or: [{},{...}]}
$and: 与运算
$not：非运算
$nor：反运算，返回不符指定条件的所有文档
查找Age=20,40或者age=20,40的记录
> db.students.find({$or:[{Age:{$in: }},{age:{$in: }}]})
{ "_id" : ObjectId("587bd2f0a954a5d5a876fb25"), "name" : "jerry", "age" : 40, "gender" : "M" }
{ "_id" : ObjectId("587bd9bfa954a5d5a876fb27"), "name" : "Yang Guo", "Age" : 20, "Course" : "Meinv Quan" }
{ "_id" : ObjectId("587bd9f4a954a5d5a876fb28"), "name" : "Guo Jing", "Age" : 40, "Course" : "Xianglong Shibazhang" }
查看有Gender字段的文档：
> db.students.find({gender: {$exists: true}})
{ "_id" : ObjectId("587bd2f0a954a5d5a876fb25"), "name" : "jerry", "age" : 40, "gender" : "M" }
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