MongoDB's Find details (i)

1. Specify the key to return

Db. [Documentname].find ({condition},{key specified})

Data Preparation Persons.json

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])
}

1.1 The specified key for all data is queried (name, age, country)

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

2. Query criteria

2. Query criteria

2.1 Check out students aged between 25-27 years

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

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

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

3. Contains or does not contain

$in or $nin

2.3 Enquiries about nationality is Chinese or American student information

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

2.4 Enquiries about nationality is not a student information in China or USA

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

4.OR Query

$or

2.4 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})

5.Null

Add new key sex to Chinese students

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

2.5 query for a student with sex equal to null

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

6. Regular queries

2.6 Find information about students with "Li" in their names

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

7. Use of $not

$not can be used anywhere to reverse the operation

2.7 Find information about students whose name does not exist in "Li"

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.

8. Array query $all and index applications

2.8 Queries students who like to see Mongod and JS

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

2.9 Query The second book is the Learning information of Java

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

9. Querying a specified length array $size it cannot be used with a comparison query (this is a disadvantage)

2.8 The number of books I like is 4 students

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

2.9 Students who like more than 3 books

1. Increase the field size

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

2. 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}})

3. Using $GT Query

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

2.10 Using the shell to find out the number of books Jim likes to read

var persons = Db.persons.find ({name: "Jim"})

while (Persons.hasnext ()) {

obj = Persons.next ();

Print (Obj.books.length)

}

1.mongodb is a NoSQL database, but he's still very powerful in document queries.

2. The query is basically used in curly braces inside the update character is basically outside

3.shell is a thoroughly-bottomed JS engine, but some special operations depend on his

Each driver package to complete (java,node. Msn

Db.persons.find ({age: {$gte: $lte: 27}},{"_id": ObjectId ("53ffe4a7504a4886bc371029"), age:1}) for students aged between 25-27 years Find out the math scores of all students who are not Korean Db.persons.find ({country: {$ne: "Korea"}},{"_id": ObjectId ("53ffe4a7504a4886bc371029"), age:1} )//Query nationality is Chinese or American student information Db.persons.find ({country:{$in: ["USA", "China"]})//Query nationality is not Chinese or American student information Db.persons.find ({country:{ $nin: ["USA", "China"]})//query for student information with a language score greater than 85 or English greater than 90 db.persons.find ({$or: [{c:{$gte: 85}},{e:{$gte: 90}}]},{_id:0,c:1 , e:1})//Add a new key to Chinese nationality sexdb.persons.update ({country: "China"},{$set: {sex: "MS"}},false,true) db.persons.update ({ Country: "USA"},{$set: {set: "MS"}},true,true) db.persons.update ({country: "China"},{$set: {sex: "M"}},false,true) Db.persons.update ({age:27},{$set: {status: "A"}},{Multi:true})//query out the sex equals null student Db.persons.find ({sex:{$in: [null ]}},{COUNTRY:1})//query out the name of the student with "Li" information, regular query Db.persons.find ({name:/li/i},{_id:0,name:1})//query out the name does not exist "Li" The student's information Db.persons.find ({name:{$not:/li/i}},{_id:0,name:1})//query likes to see Mongod and JS students Db.persons.find ({books:{$all: [" Mongobd"," JS "]}},{books:1," _id ": ObjectId (" 53ffe4a7504a4886bc371029 ")})//query likes to see Mongod and JS students Db.persons.find ({" Books.1 ":" JAVA "})//query out the number of books you like is 4 student Db.persons.find ({books:{$size: 4}},{_id:0,books:1})//Add field sizedb.persons.update ({},{$ Set:{size:4}},false,true) db.persons.update ({name: "Tom"},{$push: {books: "ORACLE"}, $inc: {size:1}})//use $ GT Query Db.persons.find ({size:{$gt: 4})//Use the shell to find out the number of books Jim likes to read var persons = Db.persons.find ({name: "Jim"}) while ( Persons.hasnext ()) {obj = Persons.next ();p rint (Obj.books.length)}

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Mark Fan (Small idea) Source: http://cube.cnblogs.com
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MongoDB's Find details (i)