MongoDB Basic Database Operations Tutorial

0. Target

Be familiar with some basic operations of MongoDB on the command line, and prepare for the next node.js operation MongoDB.

If you have ever studied or contacted a relational database (such as MySQL, SQL Server, etc.), then when reading this article, you can do the following:

Table (table)-> Collection (set)

Log (record)-> document (documentation)

Of course, this correspondence is not accurate, because the structure of table (table) is fixed, and collection (set) is not, log (record) of "Row", and document (documents) structure is more diverse. But for beginners, such metaphors can be used more quickly; in fact, the structure and operation of the document database MongoDB is similar to that of relational databases such as MySQL.

If you have never studied the database, then suggest you first look at the opening article introduced the book "MongoDB authoritative Guide", as well as the reference book "NoSQL Database Technology Combat", first on the concept of the non-relational database has an understanding, then look at this article.

If you have studied MongoDB database, then the right to review, if there are errors, please correct me. If you are already a great God, then you are more welcome to your guidance.

1. Connecting to the database

Before you connect to the database, verify that the MongoDB service is turned on. Please refer to the previous section for details.

Open the command line in the MongoDB directory, enter Mongodb\bin, and type the command MONGO

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C:\mongodb\bin>mongo

Enter MongoDB

2. Switch databases

The default shell is connected to the localhost test library for this computer, as you can see in the picture above that the database currently in use (Connecting to:) is "test"

If you want to switch the database, you can enter the following command

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Use MyDB

The mydb above is the name of the database to switch

3. Insert a record

Switch to Database Myfirstdb

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Use Myfirstdb

switching databases

Create object A,b and save them separately

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Create Object A,b A = {name: "user1"}; b = {name: "User2"}; Save Object A,b Db.user.save (a); Db.user.save (b);

Execution results

Viewing results with visual tools

Mongocola View Results

Notice that we didn't create a database named Myfirstdb before, and we didn't create a collection called user, but why is the command still able to execute and get the results we expected? This is because MongoDB, as a document-type database , is a database without a table structure, and it does not need to define a table structure beforehand.

It is this feature that MongoDB has faster processing speed than relational databases, and it also reduces the overhead required to add table structure changes such as fields. In this way, we don't have to care about the consistency between the table structure and the program; In short, it is when you add a field to a program that you do not have to consider whether the database has this field, because MongoDB will automatically create it for you.

4. Insert a record that is a little more complex

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c = {name: "User2", Card: "KK8566"}; Db.user.save (c);

Here, we added a field "card" that didn't exist before, so what about the implementation?

Look at the console first.

And look at visual management tools

Mongocola View Results

A card field has been generated automatically.

5. Modify the Record

In the previous example, we saw two "User2", and now we're going to change the last one to "User3."

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Db.user.update ({name: "User2", Card: "KK8566"}, {$set: {name: ' User3 ', Card: "KK8566"});

Modify Result:

Modify Results

Mongocola View Results

6. Delete records

We delete the first document

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Db.user.remove ({name: "user1"})

Delete

Mongocola View Results

7. Query Records

List all records

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Db.user.find ();

As you can see, there are only two documents left in the database for the delete command we executed in the previous section.

Use while to output

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var cursor = Db.user.find (); while (Cursor.hasnext ()) Printjson (Cursor.next ());

Bulk output through while

Convert to Array

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var arr = Db.user.find (). ToArray (); ARR[1]; Display a 1th

Array

In fact, we use a similar approach when we operate MongoDB on the Node.js server side.

8. Condition Inquiry

Using MONGODB query statement to implement MySQL conditional query statement: SELECT * from user WHERE name= "User3"

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Db.user.find ({name: "User3"}). ForEach (Printjson);

Conditional query

The above command returns all documents that meet the criteria, and to save costs, you can use FindOne () to get the first document that satisfies the criteria:

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Db.user.findOne ({name: "User3"});

Note that this is just a simple condition limit. We have a lot of complex requirements in practical applications, and in MySQL we use multiple and or or to represent relationships with and OR. In MongoDB, there are also keywords similar to and OR or, but in MongoDB, everything is expressed in a JSON-like format. The specific operation I will do in the following article detailed introduction, Welcome to read.

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9. Limit the number of result sets

Add limit (num) after the query statement

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Db.user.find (). limit (3); Limit to 3 documents

at this point, there are so many mongodb operations, and there are more advanced operations that will be listed in subsequent articles