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Database Study Note: Four Basic MongoDB Commands You Should Know


MongoDB is one of the most popular database with Node.js and Express.js. It is a NoSQL database.

From Google Image
Firstly, we need to install MongoDB in our server. The course TA created a good installation tutorial video on YouTube.

Since the MongoDB has updated its system. In the installation, we need to set up the Ubuntu 16.04 (Xenial) code instead of 14.04 version which is shown on the video.

 Once we finish the installation, we need to call "./mongod" and run the code, then open a new terminal window, and call "mongo", then you are ready to use Mongo shell, which is like JavaScript console. 

We can type "help" to learn the main MongoDB commands and their explanation. 

After I learned this lecture, I summarized four basic MongoDB commands to do with your database: insert, find, update and remove.

Insert

I want to create a student databases which include student name and GPA score. I can use insert command to create the new data: db.students.insert({name: "Mary", GPA: "3.5"}).


In the code, "db" is the database we are on. "Students" is the collection, and "insert" is the command that will insert data into this students collection in the database.

I insert in an object with the student name "Mary" and GPA "3.5". If  I want to see the collection name, I can simple type "show collections". It gives me the "Students".



Find

To prove that the students collection is created, I use "find" to view the data: db.students.find().


Then, you can see the data in students collection with unique Mongo ID.

I insert a new student data, and then use the find command to view all the data.


If I only want to find the student with name equal to "Mary", I can type an object inside the find command: db.students.find({name: "Mary"}). It will give me all the data related to Mary.


Update

 If I want to update an existing student data by change the name "Mike" to "Tom", I could use update command: db.students.update({name: "Mike"}, {$set {name: "Tom"}})


Update takes two different things: the first one is something we select by. In this case, I select the student name "Mike". The second thing is how we want to update. I updated the name to "Tom".

Then, I call find command to see the new data. I can see the new name "Tom" has updated successfully.

Remove

If I want to remove the data, I can use remove command: db.students.remove({name: "Mary"}). Inside the remove, I can put the student name or GPA or ID to remove the data.


Remove will remove everything matches whatever you provide by default.






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