Kako započeti s MongoDB-om za 10 minuta

Programiranje

MongoDB je bogata NoSQL baza podataka orijentirana na dokumente.

Ako ste potpuni početnik NoSQL-a, preporučujem vam da brzo pogledate moj prethodno objavljeni članak o NoSQL-u.

Danas sam želio podijeliti neke osnovne stvari o MongoDB naredbama poput upita, filtriranja podataka, brisanja, ažuriranja i tako dalje.

Ok, dosta priče, krenimo na posao!

Konfiguracija?

Da biste mogli raditi s MongoDB-om, prvo morate instalirati MongoDB na svoje računalo. Da biste to učinili, posjetite službeni centar za preuzimanje i preuzmite verziju za svoj određeni OS. Evo, koristio sam Windows.

Nakon preuzimanja postavki poslužitelja zajednice MongoDB, proći ćete postupak instalacije "sljedeće nakon sljedećeg". Kad završite, prijeđite na C pogon u koji ste instalirali MongoDB. Idite na programske datoteke i odaberite direktorij MongoDB.

C: -> Program Files -> MongoDB -> Server -> 4.0(version) -> bin

U direktoriju bin pronaći ćete zanimljivih nekoliko izvršnih datoteka.

  • mongod
  • mongo

Razgovarajmo o ove dvije datoteke.

mongod je kratica za "Mongo Daemon". mongod je pozadinski postupak koji koristi MongoDB. Glavna svrha mongoda je upravljanje svim zadacima MongoDB poslužitelja. Na primjer, prihvaćanje zahtjeva, odgovaranje na klijenta i upravljanje memorijom.

mongo je ljuska naredbenog retka koja može komunicirati s klijentom (na primjer, administratori sustava i programeri).

Sada da vidimo kako možemo pokrenuti i pokrenuti ovaj poslužitelj. Da biste to učinili u sustavu Windows, prvo morate stvoriti nekoliko direktorija na vašem C pogonu. Otvorite naredbeni redak unutar pogona C i učinite sljedeće:

C:\> mkdir data/dbC:\> cd dataC:\> mkdir db

Svrha ovih direktorija je MongoDB zahtijeva mapu za pohranu svih podataka. Zadana putanja direktorija podataka MongoDB-a je /data/dbna pogonu. Stoga je neophodno da te direktorije pružimo tako.

Ako pokrenete MongoDB poslužitelj bez tih direktorija, vjerojatno ćete vidjeti sljedeću pogrešku:

Nakon stvaranja te dvije datoteke, vratite se opet u mapu bin u vašem mongodb direktoriju i otvorite svoju ljusku unutar nje. Pokrenite sljedeću naredbu:

mongod

Voilà! Sada je naš MongoDB poslužitelj pokrenut i pokrenut! ?

Da bismo mogli raditi s ovim poslužiteljem, potreban nam je posrednik. Dakle, otvorite drugi naredbeni prozor unutar mape za povezivanje i pokrenite sljedeću naredbu:

mongo

Nakon pokretanja ove naredbe, idite do ljuske koju smo pokrenuli mongod naredba (koja je naš poslužitelj). Na kraju ćete vidjeti poruku "Prihvaćena je veza". To znači da su naša instalacija i konfiguracija uspješni!

Jednostavno pokrenite u mongo ljusci:

db

Postavljanje varijabli okoline

Da biste uštedjeli vrijeme, možete postaviti varijable svog okruženja. U sustavu Windows to se radi slijedeći donje izbornike:

Advanced System Settings -> Environment Variables -> Path(Under System Variables) -> Edit

Jednostavno kopirajte put do naše mape bin i pritisnite OK! U mom slučaju jestC:\Program Files\MongoDB\Server\4.0\bin

Sad ste spremni!

Suradnja s MongoDB-om

Postoji hrpa GUI-a (grafičko korisničko sučelje) za rad s MongoDB poslužiteljem kao što su MongoDB Compass, Studio 3T i tako dalje.

Oni pružaju grafičko sučelje tako da možete lako raditi s bazom podataka i izvoditi upite umjesto da koristite ljusku i ručno upisujete upite.

Ali u ovom ćemo članku za obavljanje posla koristiti naredbeni redak.

Sada je vrijeme da zaronimo u MongoDB naredbe koje će vam pomoći da ih koristite sa svojim budućim projektima.

  1. Otvorite naredbeni redak i upišite mongodza pokretanje MongoDB poslužitelja.

2. Otvorite drugu ljusku i upišite mongoza povezivanje s MongoDB poslužiteljem baze podataka.

1. Pronalaženje trenutne baze podataka u kojoj se nalazite

db

Ova naredba će prikazati trenutnu bazu podataka u kojoj se nalazite. testPočetna je baza podataka koja dolazi prema zadanim postavkama.

2. Popis baza podataka

show databases

Trenutno imam četiri baze podataka. To su: CrudDB, admin, configi local.

3. Idite na određenu bazu podataka

use

Here I’ve moved to the local database. You can check this if you try the command dbto print out the current database name.

4. Creating a Database

With RDBMS (Relational Database Management Systems) we have Databases, Tables, Rows and Columns.

But in NoSQL databases, such as MongoDB, data is stored in BSON format (a binary version of JSON). They are stored in structures called “collections”.

In SQL databases, these are similar to Tables.

Alright, let’s talk about how we create a database in the mongo shell.

use

Wait, we had this command before! Why am I using it again?!

In MongoDB server, if your database is present already, using that command will navigate into your database.

But if the database is not present already, then MongoDB server is going to create the database for you. Then, it will navigate into it.

After creating a new database, running the show database command will not show your newly created database. This is because, until it has any data (documents) in it, it is not going to show in your db list.

5. Creating a Collection

Navigate into your newly created database with the usecommand.

Actually, there are two ways to create a collection. Let’s see both.

One way is to insert data into the collection:

db.myCollection.insert({"name": "john", "age" : 22, "location": "colombo"})

This is going to create your collection myCollectioneven if the collection does not exist. Then it will insert a document with nameand age. These are non-capped collections.

The second way is shown below:

2.1 Creating a Non-Capped Collection

db.createCollection("myCollection")

2.2 Creating a Capped Collection

db.createCollection("mySecondCollection", {capped : true, size : 2, max : 2})

In this way, you’re going to create a collection without inserting data.

A “capped collection” has a maximum document count that prevents overflowing documents.

In this example, I have enabled capping, by setting its value to true.

The size : 2 means a limit of two megabytes, and max: 2 sets the maximum number of documents to two.

Now if you try to insert more than two documents to mySecondCollection and use the find command (which we will talk about soon), you’ll only see the most recently inserted documents. Keep in mind this doesn’t mean that the very first document has been deleted — it is just not showing.

6. Inserting Data

We can insert data to a new collection, or to a collection that has been created before.

There are three methods of inserting data.

  1. insertOne() is used to insert a single document only.
  2. insertMany() is used to insert more than one document.
  3. insert() is used to insert documents as many as you want.

Below are some examples:

  • insertOne()
db.myCollection.insertOne( { "name": "navindu", "age": 22 } )
  • insertMany()
db.myCollection.insertMany([ { "name": "navindu", "age": 22 }, { "name": "kavindu", "age": 20 }, { "name": "john doe", "age": 25, "location": "colombo" } ])

The insert() method is similar to the insertMany() method.

Also, notice we have inserted a new property called locationon the document for John Doe. So if youusefind, then you’ll see only forjohn doe the locationproperty is attached.

This can be an advantage when it comes to NoSQL databases such as MongoDB. It allows for scalability.

7. Querying Data

Here’s how you can query all data from a collection:

db.myCollection.find()

If you want to see this data in a cleaner, way just add .pretty()to the end of it. This will display document in pretty-printed JSON format.

db.myCollection.find().pretty()

Wait...In these examples did you just notice something like _id? How did that get there?

Well, whenever you insert a document, MongoDB automatically adds an _id field which uniquely identifies each document. If you do not want it to display, just simply run the following command

db.myCollection.find({}, _id: 0).pretty()

Next, we’ll look at filtering data.

If you want to display some specific document, you could specify a single detail of the document which you want to be displayed.

db.myCollection.find( { name: "john" } )

Let’s say you want only to display people whose age is less than 25. You can use $lt to filter for this.

db.myCollection.find( { age : {$lt : 25} } )

Similarly, $gt stands for greater than, $lte is “less than or equal to”, $gte is “greater than or equal to” and $ne is “not equal”.

8. Updating documents

Let’s say you want to update someone’s address or age, how you could do it? Well, see the next example:

db.myCollection.update({age : 20}, {$set: {age: 23}})

The first argument is the field of which document you want to update. Here, I specify age for the simplicity. In production environment, you could use something like the _id field.

It is always better to use something like _id to update a unique row. This is because multiple fields can have same age and name. Therefore, if you update a single row, it will affect all rows which have same name and age.

If you update a document this way with a new property, let’s say location for example, the document will be updated with the new attribute. And if you do a find, then the result will be:

If you need to remove a property from a single document, you could do something like this (let’s say you want ageto be gone):

db.myCollection.update({name: "navindu"}, {$unset: age});

9. Removing a document

As I have mentioned earlier, when you update or delete a document, you just need specify the _id not just name, age, location.

db.myCollection.remove({name: "navindu"});

10. Removing a collection

db.myCollection.remove({});

Note, this is not equal to the drop() method. The difference is drop() is used to remove all the documents inside a collection, but the remove() method is used to delete all the documents along with the collection itself.

Logical Operators

MongoDB provides logical operators. The picture below summarizes the different types of logical operators.

Let’s say you want to display people whose age is less than 25, and also whose location is Colombo. What we could do?

We can use the $andoperator!

db.myCollection.find({$and:[{age : {$lt : 25}}, {location: "colombo"}]});

Last but not least, let’s talk aboutaggregation.

Aggregation

A quick reminder on what we learned about aggregation functions in SQL databases:

Simply put, aggregation groups values from multiple documents and summarizes them in some way.

Imagine if we had male and female students in a recordBook collection and we want a total count on each of them. In order to get the sum of males and females, we could use the $group aggregate function.

db.recordBook.aggregate([ { $group : {_id : "$gender", result: {$sum: 1}} } ]);

Wrapping up

So, we have discussed the basics of MongoDB that you might need in the future to build an application. I hope you enjoyed this article – thanks for reading!

If you have any queries regarding this tutorial, feel free to comment out in the comment section below or contact me on Facebook or Twitter or Instagram.

See you guys in the next article! ❤️ ✌?

Link to my previous article: NoSQL