MongoDB's mongo shell common operation methods and operation script notes

1. Common commands

1, Help view command prompt

help

db.help();

db.yourColl.help();

db.youColl.find().help();

rs.help();

2. Switch/create database

use yourDB; The current database is automatically created when a collection (table) is created
3. Query all databases

show dbs;

4. Delete the database currently in use

db.dropDatabase();

5, clone database from specified host

db.cloneDatabase( " 127.0.0.1 " ); 

Clones data from the database 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 native mydb data to the temp database
7. Fix the current database

db.repairDatabase();

8. View the database you are currently using

db.getName();

db; The db and getName methods are one effect of querying the currently used database
9. Display the current db status

db.stats();

10. Current VERSION of db

db.version();

11. View the machine address of the current db link

db.getMongo();

2. Collection(table) aggregate collection

1. Create an aggregation collection (table)

show dbs;

0

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

db.getCollection("account");

3. Obtain all the aggregate sets of the current db

db.getCollectionNames();

4. Display the current status of all db clustered indexes

show dbs;

3

3. User relevance

1. Add 1 user

show dbs;

4

Add user, set password, read-only
2. Display all current users

show dbs;

5

3. Delete users

show dbs;

6

These are some of the most basic commands that I'll use as notes. I haven't even tried crud, but I'll wait until I do.

Statement block operation

1. Simple Hello World

print("Hello World!");

This method calls the print function, and directly writes "Hello World!" The effect of theta is 1;

2. Convert 1 object to json

tojson(new Object());

tojson(new Object('a'));

3, loop to add data

show dbs;

9

This adds 30 pieces of data to the loop, and you can also omit the parenthesis

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

It is also possible. When you use ES108en. users. find() to query, you can use it to view the information on the next page if multiple data are displayed and one page cannot be displayed.

4. find cursor query

var cursor = db.users.find();

while (cursor.hasNext()) {

printjson(cursor.next());

}

This queries all users information and can be written as follows

var cursor = db.users.find();

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

You can also omit the {} sign

5. forEach iteration cycle

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

One function must be passed in forEach to process the data information for each iteration

6. Treat find cursor as an array

var cursor = db.users.find();

cursor[4];

Gets the data with a subscript index of 4

Since you can treat it as an array, you can get its length: cursor.length (); Or cursor. count ();

That way we can also display the data in a loop

for (var i = 0, len = c.length(); i < len; i++) printjson(c[i]);

7. Convert find cursor to array

var arr = db.users.find().toArray();

printjson(arr[2]);

Convert it to an array using the toArray method

8. Customize our own query results

Show only the age < = 28 and displays only the age column

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));});

other

1, query the previous error information

db.getPrevError();

2. Clear the error record

db.resetError();

3. Display database list

show dbs

4. Display collections in current database (similar to tables in relational database)

show collections

5. Display users

show users

6. Switch the current database, which is the same as es186EN-SQL

use