MongoDB 查询文档(四)

如果数据库中尚未有数据, 准备测试数据

db.test1.insertMany([     {"name":"zhangsan","age":19,"score": [90,80]},     {"name":"lisi","age":29,"score": [40,60]},     {"name":"xiaoming","age":18,"score": [20,40]},     {"name":"xiaohong"} ])

第一部分元素操作符

1.$exists: 判断指定字段是否存在,并返回相应的结果2.$type: 匹配字段对应的类型

1.1$exists

{field: { $exists: } }

判断指定字段是否存在,并返回相应的结果, 直接上代码

{"$exists": true}

> db.test1.find({"qty": {"$exists":true}})#张三存在qty属性, 就返回该条数据{"_id": ObjectId("58c8dc54ef9b994487420f29"),"name":"zhangsan","age": 19,"score": [ 90, 80 ],"qty": 10 }

{"$exists": false}

> db.test1.find({"qty": {"$exists":false}})#以下三条数据均不存在qty字段{"_id": ObjectId("58c8dc54ef9b994487420f2a"),"name":"lisi","age": 29,"score": [ 40, 60 ] } {"_id": ObjectId("58c8dc54ef9b994487420f2b"),"name":"xiaoming","age": 18,"score": [ 20, 40 ] } {"_id": ObjectId("58c9e4b80c4d4cf6f4563b26"),"name":"xiaohong"}

1.2 $type

$type文档

{field: { $type: | } }

第二部分

1.$mod模运算2.$regex    正则表达3.$text    文本搜索4.$where: 支持js表达式

2.1 $mod运算

db.users.find('this.age % 6 == 0');  或者  > db.users.find({"age": {$mod : [6,0]}}); {"_id": ObjectId("58d21667edca14f0f7ffbedb"),"name":"xiaoming","age":18,"score": [20,40] }

2.2 $regex正则表达

匹配正则表达式

注: 之后后专门整理一篇正则表达式的文章

2.3 $text

全文本搜索

2.4 where