MongoDB CRUD: Part I

In a previous post, I wrote the "M" in MEAN really stands for Mongoose as it is the de facto way to work with MongoDB. However, it's interesting to peek beneath the surface. You don't have to be able to rebuild a manifold in order to drive, but you should probably know how to check the oil.

So, now that we know how to connect, let's figure out how to CRUD documents.

Create

Databases contain collections. Collections contain documents. To insert a new document into a collection, we use the insert method.

db.stomach.insert({
    crust: 'thin',
    pepperoni: true,
    olives: true,
    anchovies: 6
});

Easy, right? That inserted a pizza-like document into the stomach collection. Let's try it again.

db.stomach.insert({
    beer: 'Sweetwater',
    count: 2
});

Pretty straightforward. Also, this demonstrates why NoSQL databases are so cool; documents within a collection don't have to have to the same fields. Collections are like tables, but friendlier. Do you remember going into admin mode and creating the stomach table before we ran these queries?

Exactly.

Read

Now that's we've got a collection and a couple documents, let's see about reading them. What was our collection's name again?

> show collections
stomach
system.indexes

Oh, yeah, stomach. Let's see what's in there.

> db.stomach.find().pretty();
{
    "_id" : ObjectId("5424a39628f262081e997a7e"),
    "crust" : "thin",
    "pepperoni" : true,
    "olives" : true,
    "anchovies" : 6
}
{
    "_id" : ObjectId("5424a5ba28f262081e997a7f"),
    "beer" : "Sweetwater",
    "count" : 2
}

As you can see, MongoDB inserted a unique _id for us because we didn't include one.

find can take a couple arguments to make it more useful.

• an object of query operators - This specifies what documents you're looking for.
• an object of projection operators - This specifies what fields you want returned in the results.

db.stomach.find(
    {
        anchovies: {
            $exists: true
        }
    },

    {
        crust: 1,
        pepperoni: 1,
        donkey: 1
    }
);

I'm not going to go over all the options as the documentation is very good, but you get the idea. A couple notes, though.

• It's worth noting that find returns a cursor that you can iterate through to see the returned documents. Because we didn't assign the expression to a variable, mongo printed out the first 20 results automatically.
• _id is returned unless you explicitly exclude it in the projection. You can't mix includes and excludes in your projection with the exception of the _id field.
• We included donkey in the projection, but it doesn't exist. Therefore, it was not in the result.

Summary

My wife just turned on Bill a Ted and it's surprisingly distracting. That means, Update and Delete will come in part II of this post. Party on, dudes!

References

• From within mongo, just type help. It's very good.
• MongoDB CRUD operations
• MongoDB Glossary
• MongoDB Create
• MongoDB Read
• mongo shell reference

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Check out the accompanying Github repo to these posts about MongoDB/Mongoose.