MongoDB Query operation

1 Data preparation

var persons = [{
Name: "Jim",
AGE:25,
Email: "[email protected]",
c:89,m:96,e:87,
Country: "USA",
books:["JS", "C + +", "ExtJS", "MONGODB"]
},
{
Name: "Tom",
AGE:25,
Email: "[email protected]",
C:75,M:66,E:97,
Country: "USA",
books:["PHP", "JAVA", "ExtJS", "C + +"]
},
{
Name: "Lili",
Age:26,
Email: "[email protected]",
C:75,M:63,E:97,
Country: "USA",
books:["JS", "JAVA", "C #", "MONGODB"]
},
{
Name: "Zhangsan",
Age:27,
Email: "[email protected]",
C:89,m:86,e:67,
Country: "China",
books:["JS", "JAVA", "ExtJS", "MONGODB"]
},
{
Name: "Lisi",
Age:26,
Email: "[email protected]",
c:53,m:96,e:83,
Country: "China",
books:["JS", "C #", "PHP", "MONGODB"]
},
{
Name: "Wangwu",
Age:27,
Email: "[email protected]",
C:45,m:65,e:99,
Country: "China",
books:["JS", "JAVA", "C + +", "MONGODB"]
},
{
Name: "Zhaoliu",
Age:27,
Email: "[email protected]",
C:99,M:96,E:97,
Country: "China",
books:["JS", "JAVA", "ExtJS", "PHP"]
},
{
Name: "Piaoyingjun",
Age:26,
Email: "[email protected]",
C:39,m:54,e:53,
Country: "Korea",
books:["JS", "C #", "ExtJS", "MONGODB"]
},
{
Name: "Lizhenxian",
Age:27,
Email: "[email protected]",
C:35,m:56,e:47,
Country: "Korea",
books:["JS", "JAVA", "ExtJS", "MONGODB"]
},
{
Name: "Lixiaoli",
Age:21,
Email: "[email protected]",
C:36,M:86,E:32,
Country: "Korea",
books:["JS", "JAVA", "PHP", "MONGODB"]
},
{
Name: "Zhangsuying",
Age:22,
Email: "[email protected]",
C:45,m:63,e:77,
Country: "Korea",
books:["JS", "JAVA", "C #", "MONGODB"]
}]
for (var i = 0;i<persons.length;i++) {
Db.persons.insert (Persons[i])
}
var persons = Db.persons.find ({name: "Jim"})

2 Query 2.1 queries out the specified key for all data (name, age, country)

Db.persons.find ({},{name:1,age:1,country:1,_id:0})

2.2 Query criteria

Check out students aged between 25-27 years

Db.persons.find ({age: {$gte: $lte: 27},{_id:0,age:1})

Find out the math scores of all students who are not Korean

Db.persons.find ({country:{$ne: "Korea"}},{_id:0,m:1})

2.3 Contains or does not contain: $in or $nin

Check nationality is a student's information in China or USA

Db.persons.find ({country:{$in: ["USA", "China"]})

Check nationality is not a Chinese or American student information

Db.persons.find ({country:{$nin: ["USA", "China"]})

2.4 or query: $or

Enquiries about students with language scores greater than 85 or English greater than 90

Db.persons.find ({$or: [{c:{$gte: 85}},{e:{$gte: 90}}]},{_id:0,c:1,e:1})

2.5 Null

Add new key sex to Chinese students

Db.person.update ({country: "China"},{$set: {sex: "M"}})

Query for students with sex equal to null

Db.persons.find ({sex:{$in: [Null]}},{country:1})

2.6 Regular queries

Find information about students with "Li" in their names

Db.persons.find ({name:/li/i},{_id:0,name:1})

The use of 2.7 $not, $not can be used anywhere to take the reverse operation

Find information about students who do not have "Li" in their name

Db.persons.find ({name:{$not:/li/i}},{_id:0,name:1})

The difference between $not and $nin is that $not can be used anywhere, $nin is used on a set.

2.8 Array Query $all and index applications

Find students who like to see Mongod and JS

Db.persons.find ({books:{$all: ["MONGOBD", "JS"]}},{books:1,_id:0})

Query the second book is the Learning information of Java

Db.persons.find ({"Books.1": "JAVA"})

Queries the specified length array $size it cannot be used with comparison queries (this is a disadvantage)

Check out the number of books you like that are 4 students

Db.persons.find ({books:{$size: 4}},{_id:0,books:1})

2.9 Students who like more than 3 books

Increase Field Size

Db.persons.update ({},{$set: {size:4}},false, True)

Change the way books are updated, size increases by 1 each time you add a book

Db.persons.update ({},{$push: {books: "ORACLE"}, $inc: {size:1}})

Using $GT Query

Db.persons.find ({size:{$gt: 3}})

2.10 $slice operator returns the internal value of the specified array in the document

Find out the 2nd to 4th book in Jim's Bookshelf

Db.persons.find ({name: "Jim"},{books:{"$slice": [1,3]}})

Check out the last book

Db.persons.find ({name: "Jim"},{books:{"$slice": -1},_id:0,name:1})

2.11 Document query: $elemMatch

Add a resume document to Jim

var Jim = [{
School: "K",
Score: "A"
},{
School: "L",
Score: "B"
},{
School: "J",
Score: "A +"
}]
Db.persons.update ({name: "Jim"},{$set: {school:jim}})

Check out the students who have studied at K.

Db.persons.find ({school:{$elemMatch: {school: "K", Score: "A"}})

2.12 Limit returns the specified number of data bars

Querying the first 5 data in a persons document

Db.persons.find ({},{_id:0,name:1}). Limit (5)

2.13 Skip returns the span of the specified data

Querying the data for 5~10 bars in a persons document

Db.persons.find ({},{_id:0,name:1}). Limit (5). Skip (5)

2.14. Sort returns data sorted by age [1,-1]

Db.persons.find ({},{_id:0,name:1,age:1}). Sort ({age:1})

MongoDB Query operation