mongodb的学习 （2）

1.条件查询

查询姓名为小明的学生                            db.local.find({name:'小明'});;

查询英语成绩大于90分的同学                 db.local.find({score:{$gt:90}}); //查找成绩大于90分$gt

查询数学成绩不等于88的同学                db.local.find({score:{$ne:88}});    

查询总分大于200分的所有同学              db.local.find({score:{$gt:200}});

$lt         小于   
$gt        大于
$ne       不等于

　　截图：

 2.分页

- `db.local.find().skip(3).limit(3);`

- db.集合名称.find().跳到3.显示3条

+ limit 0,3

截图：

3.排序

db.local.find().sort({key:排序方式});

例如：

升序：

> db.local.find().sort({'score':1})
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e59"), "contry" : "美国", "name" : "jack", "score" : 45 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e5a"), "contry" : "美国", "name" : "rose", "score" : 67 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e56"), "contry" : "中国", "name" : "小明", "score" : 77 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e57"), "contry" : "中国", "name" : "小红", "score" : 88 }
{ "_id" : ObjectId("5c1dd8b9b7c0cc1cfd4e2e5b"), "contry" : "美国", "name" : "mick", "score" : 89 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e58"), "contry" : "中国", "name" : "小张", "score" : 99 }

降序：
db.local.find().sort({'score':-1})
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e58"), "contry" : "中国", "name" : "小张", "score" : 99 }
{ "_id" : ObjectId("5c1dd8b9b7c0cc1cfd4e2e5b"), "contry" : "美国", "name" : "mick", "score" : 89 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e57"), "contry" : "中国", "name" : "小红", "score" : 88 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e56"), "contry" : "中国", "name" : "小明", "score" : 77 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e5a"), "contry" : "美国", "name" : "rose", "score" : 67 }
{ "_id" : ObjectId("5c1dd8b7b7c0cc1cfd4e2e59"), "contry" : "美国", "name" : "jack", "score" : 45 }

截图：

4.模糊匹配

`db.local.find({name:{$regex:'小'}});`
- `db.local.find({name:{$regex:'明'}});`