Basic use of MongoDB

After MongoDB is started successfully, open a command line window and enter mongo to perform database operations. Enter help to see the basic operation command: showdbs: display the Database List showcollections: display the set in the current database (similar to the tables in the relational database) showusers: display the user usedbname: Switch

After MongoDB is started successfully, open a command line window and enter mongo to perform database operations. Enter help to see the basic operation command: show dbs: display the Database List show collections: display the set in the current database (similar to the tables in the relational database) show users: display the user use db name: Switch

After MongoDB is started successfully, open a command line window and enter mongo to perform database operations.

Enter help to view the basic operation commands:

Show dbs: displays the Database List
Show collections: displays a set in the current database (similar to a table in a relational database)
Show users: displays users

Use : Switch the current database, which means the same as in the MS-SQL
Db. help (): displays database operation commands, which contain many commands.
Db. foo. help (): displays the set operation commands. There are also many commands. foo refers to a set named foo in the current database, not a real command.
Db. foo. find (): searches for the foo set in the current database (all data is listed due to no conditions)
Db. foo. find ({a: 1}): searches for the foo set in the current database. The condition is that the data has an attribute named a and the value of a is 1.

MongoDB does not have commands for creating databases, but similar commands are available.

For example, if you want to create a database named "myTest", run the use myTest command first and then perform some operations (such as db. createCollection ('user') to create a database named "myTest.

Common database commands

1. Help to view command prompts

Help

Db. help ();

Db. yourColl. help ();

Db. youColl. find (). help ();

Rs. help ();

2. Switch to/create a database

Use yourDB; when you create a set (table), the current database is automatically created.

3. query all databases

Show dbs;

4. Delete the currently used database

Db. dropDatabase ();

5. clone a database from a specified host

Db. cloneDatabase ("127.0.0.1"); clone the database data on the specified machine to the current database

6. Copy the specified database data from the specified machine to a database

Db. copyDatabase ("mydb", "temp", "127.0.0.1"); copy the data of mydb on the local machine to the temp database.

7. Fix the current database

Db. repairDatabase ();

8. view the currently used database

Db. getName ();

Db; the db and getName methods have the same effect. You can query the currently used database.

9. display the current db status

Db. stats ();

10. Current db version

Db. version ();

11. view the address of the linked machine of the current db

Db. getMongo ();

Collection aggregation set

1. Create an aggregation set (table)

Db. createCollection ("collName", {size: 20, capped: 5, max: 100 });

2. Get the clustering set (table) with the specified name)

Db. getCollection ("account ");

3. obtain all the aggregation sets of the current db.

Db. getCollectionNames ();

4. display the status of all clustered indexes of the current db

Db. printCollectionStats ();

User-related

1. Add a user

Db. addUser ("name ");

Db. addUser ("userName", "pwd123", true); add a user, set a password, and check whether the user is read-only

2. database authentication and security mode

Db. auth ("userName", "123123 ");

3. display all current users

Show users;

4. delete a user

Db. removeUser ("userName ");

Others

1. query previous error messages

Db. getPrevError ();

2. Clear error records

Db. resetError ();

View basic information about a collection

1. View help? Db. yourColl. help ();

2. query the number of data entries in the current set? Db. yourColl. count ();

3. view the data space size db. userInfo. dataSize ();

4. Obtain the db. userInfo. getDB () of the current collection ();

5. Get the current cluster status db. userInfo. stats ();

6. Get the total size of the clustered set db. userInfo. totalSize ();

7. Cluster set storage space size db. userInfo. storageSize ();

8. Shard version information? Db. userInfo. getShardVersion ()

9. Rename db. userInfo. renameCollection ("users") for the clustering set; rename userInfo to users

10. Delete db. userInfo. drop ();

Aggregate collection Query

1. query all records

db.userInfo.find();

Equivalent to: select * from userInfo;

By default, 20 records are displayed on each page. If no record is displayed, you can use the it iteration command to query data on the next page. Note: The it command cannot contain ";"

However, you can set the size of data displayed on each page. Use DBQuery. shellBatchSize = 50 to display 50 records on each page.

2. query duplicate data of a column in the current clustering set after Removal

db.userInfo.distinct("name");

The same data in name is filtered out.

Equivalent to: select distict name from userInfo;

3. query records with age = 22

db.userInfo.find({"age": 22});

Equivalent to: select * from userInfo where age = 22;

4. query records of age> 22

db.userInfo.find({age: {$gt: 22}});

Equivalent to: select * from userInfo where age> 22;

5. query records of age <22

db.userInfo.find({age: {$lt: 22}});

Equivalent to: select * from userInfo where age <22;

6. query records with age> = 25

db.userInfo.find({age: {$gte: 25}});

Equivalent to: select * from userInfo where age> = 25;

7. query records of age <= 25

db.userInfo.find({age: {$lte: 25}});

8. query age> = 23 and age <= 26

db.userInfo.find({age: {$gte: 23, $lte: 26}});

9. query data whose name contains mongo

db.userInfo.find({name: /mongo/});

// Equivalent to %

select * from userInfo where name like ‘%mongo%’;

10. query names starting with mongo

db.userInfo.find({name: /^mongo/});

select * from userInfo where name like ‘mongo%’;

11. query the name and age data of a specified Column

db.userInfo.find({}, {name: 1, age: 1});

Equivalent to: select name, age from userInfo;

Of course, "true" or "false" can be used for name. If "true" is used, "river name: 1" has the same effect. If "false" is used, "name" is excluded and column information other than "name" is displayed.

12. query the name and age data of a specified column. age> 25

db.userInfo.find({age: {$gt: 25}}, {name: 1, age: 1});

Equivalent to: select name, age from userInfo where age> 25;

13. sort by age

Ascending Order: db. userInfo. find (). sort ({age: 1 });

Descending order: db. userInfo. find (). sort ({age:-1 });

14. query data with name = zhangsan and age = 22

db.userInfo.find({name: 'zhangsan', age: 22});

Equivalent to: select * from userInfo where name = 'hangsan' and age = '22 ';

15. query the first five data entries

db.userInfo.find().limit(5);

Equivalent to: selecttop 5 * from userInfo;

16. Query 10 data records later

db.userInfo.find().skip(10);

Equivalent to: select * from userInfo where id not in (

selecttop 10 * from userInfo

);

17. query data between 5-10

db.userInfo.find().limit(10).skip(5);

It can be used for paging. limit is pageSize, and skip is the page * pageSize

18. or and query

db.userInfo.find({$or: [{age: 22}, {age: 25}]});

Equivalent to: select * from userInfo where age = 22 or age = 25;

19. query the first data entry.

db.userInfo.findOne();

Equivalent to: selecttop 1 * from userInfo;

db.userInfo.find().limit(1);

20. query the number of records in a result set

db.userInfo.find({age: {$gte: 25}}).count();

Equivalent to: select count (*) from userInfo where age> = 20;

21. sort by Column

db.userInfo.find({sex: {$exists: true}}).count();

Equivalent to: select count (sex) from userInfo;

Index

1. Create an index

db.userInfo.ensureIndex({name: 1});

db.userInfo.ensureIndex({name: 1, ts: -1});

2. query all indexes of the current clustered set

db.userInfo.getIndexes();

3. view the total index record size

db.userInfo.totalIndexSize();

4. Read all index information of the current set

db.users.reIndex();

5. delete a specified index

db.users.dropIndex("name_1");

6. Delete All indexes

db.users.dropIndexes();

Modify, add, and delete Set Data

1. Add

db.users.save({name: ‘zhangsan’, age: 25, sex: true});

The data column of the added data is not fixed. The data column is subject to the added data.

2. Modify

db.users.update({age: 25}, {$set: {name: 'changeName'}}, false, true);

Equivalent to: update users set name = 'changename' where age = 25;

db.users.update({name: 'Lisi'}, {$inc: {age: 50}}, false, true);

Equivalent to: update users set age = age + 50 where name = 'lisi ';

db.users.update({name: 'Lisi'}, {$inc: {age: 50}, $set: {name: 'hoho'}}, false, true);

Equivalent to: update users set age = age + 50, name = 'hohoho' where name = 'lisi ';

3. Delete

db.users.remove({age: 132});

4. query, modify, and delete

db.users.findAndModify({

    query: {age: {$gte: 25}}, 

    sort: {age: -1}, 

    update: {$set: {name: 'a2'}, $inc: {age: 2}},

    remove: true

});

db.runCommand({ findandmodify : "users", 

    query: {age: {$gte: 25}}, 

    sort: {age: -1}, 

    update: {$set: {name: 'a2'}, $inc: {age: 2}},

    remove: true

});

Update or remove is a required parameter. Other parameters are optional.

Parameter description default value query filtering condition {} sort if multiple documents meet the query filtering condition, the first object is selected in the order specified by this parameter, this object will be operated {} remove if it is true, the selected object will be deleted before the return N/A update A modifier object N/A new if it is true, the modified object instead of the original object will be returned. This parameter is ignored during the delete operation. False fields refer to Retrieving a Subset of Fields (1.5.0 +) All fields upsert to create a new object. If the query result is blank. Example (1.5.4 +) false

Statement block Operation

1. Simple Hello World

print("Hello World!");

This method calls the print function and directly writes "Hello World! "The effect is the same;

2. convert an object to json

tojson(new Object());

tojson(new Object('a'));

3. Add data cyclically

> for (vari= 0;i<30;i++) {

... db.users.save({name: "u_" + i, age: 22 + i, sex: i % 2});

... };

In this way, 30 pieces of data are added cyclically, and the brackets can also be omitted.

> for (vari= 0;i<30;i++) db.users.save({name: "u_" + i, age: 22 + i, sex: i % 2});

You can also use it to view information on the next page when you use db. users. find () to query multiple data entries and cannot display one page;

4. find cursor Query

>varcursor = db.users.find();

> while (cursor.hasNext()) { 

    printjson(cursor.next()); 

}

In this way, all users information can be queried.

varcursor = db.users.find();

while (cursor.hasNext()) { printjson(cursor.next); }

You can also omit the {} number.

5. forEach iteration Loop

db.users.find().forEach(printjson);

In forEach, a function must be passed to process the data information of each iteration.

6. process the find cursor as an array

varcursor = db.users.find();

cursor[4];

Obtain the data with the subscript index 4.

Since it can be processed as an array, We can get its length: cursor. length (); or cursor. count ();

In this way, we can also display data cyclically.

For (vari = 0, len = c. length (); I
 
  
7. Convert the find cursor to an array
  
>var arr = db.users.find().toArray();
  
> printjson(arr[2]);
  
Convert toArray to an array
  
8. customize our own query results
  
Only show age <= 28 and only show age data
  
db.users.find({age: {$lte: 28}}, {age: 1}).forEach(printjson);
  
db.users.find({age: {$lte: 28}}, {age: true}).forEach(printjson);
  
Exclude age Columns
  
db.users.find({age: {$lte: 28}}, {age: false}).forEach(printjson);
  
9. forEach transfer function display information
  
db.things.find({x:4}).forEach(function(x) {print(tojson(x));});
  
    
  
Original article address: apsaradb for MongoDB is basically used. Thank you for sharing it with the original author.