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Welcome back, everyone, to this lecture on reading and querying with your database.

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Each model you create comes with a manager that allows you to create what's known as a query set, which

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can then be used to retrieve entries from the database.

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Keep in mind that the query set is actually lazily evaluated, meaning that it doesn't hit the database

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until it's explicitly asked to grab the information.

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Which is nice because you don't want to ping your database for every extra filter that you add on to

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your query set.

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This will make more sense when we get into more advanced filtering techniques.

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So recall that previously we use something like my model, the objects in order to create or bulk creates

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entries.

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This is known as the Django model manager or just manager for short.

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This manager can then actually read the database through the use of different method calls in the same

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way it could create entries also through the use of method calls.

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There are the call and get method calls to actually retrieve and get the information from the database.

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And then you can also narrow down results with method calls like that filter and that exclude.

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And what's nice about this manager and the query set is just putting in that filter in that exclude

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do not explicitly call the database.

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It's not until you actually call for something like it, thought all or thought get that the database

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is hit with the request.

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So in this particular election, we're really just going to focus on the Dot all method, which allows

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us to grab all the entries in the database table.

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Typically, we won't want everything in a database table, so we'll need to filter our results, but

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we'll discuss filtering in more detail later on in the next lecture.

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For right now, we're really just exploring how do we grab everything from a table and what does that

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information actually look like?

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A general great resource on queries of examples can be found at Jingo Project com under the DB or database

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section under queries.

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That's really where we're referencing for the next series of lectures.

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For right now, we want to explore the very basics of reading and data that is all the entries in a

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tables entry points.

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And then what changes we can make to make the model actually have results that are more human readable.

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So let's head over to the code editor.

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OK, so here I am back inside Visual Studio code.

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I'm going to launch my shell again.

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Which remember is Python managed the pie shell.

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Go ahead and enter there.

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And again, because I'm using interactive python.

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If I python, because that's how I configured things in my computer, I get to see the input output.

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But yours may just be just a plain python shell.

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That's totally OK.

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So.

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Remember, I want to actually get access to the patient model, which means I need to import actually

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say from.

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And then office, the models, import patients.

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OK, so now I have patients available to us.

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Now we're going to do is we're actually going to query this database and see what happens.

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So the simplest way to do this is by simply saying patient objects.

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And this is the manager.

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The manager can then actually get a query set, and the simplest query is to simply just request give

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me all the objects or entries in this particular table or database.

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And this returns back a query set that looks a lot like a list.

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So you get back this query set.

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It is kind of like a list in the sense that you can actually index things from this.

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So for example, if you only wanted, let's say, the first item, you could put brackets there for

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zero and then it would just return back the first patient.

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So notice it does have some sort of primary I.D. or primary care.

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One, two, three or four or five, et cetera.

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But you're probably wondering, well, what's the deal?

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Why is there more information about the first name, last name or age?

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Well, recall appear in our model.

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There is no human readable screen representation of this class.

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And in fact, you would get this for any object you attempted to print out in Python that didn't have

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a string method attached to it.

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So let's add that in so that it's more readable for us.

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We're going to say the E.F. underscore underscore S.T.A.R. underscore underscore percent self.

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And now we're just going to return whatever the string representation we want for this particular model

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object this.

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So I'm going to use string literal formatting here.

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And let's say that I want to report back the last name, first comma, first name again.

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It's kind of up to you.

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So we'll say solved that last name.

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And then I'm also going to say soft first name, and let's put a comma here.

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And let's say is and then let's report their age, self-taught, eight years old.

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OK, so this is kind of a long string representation, but hopefully you get the idea.

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You can obviously edit this to whatever's most convenient.

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Not sure if it's really necessary to say their age when we report back patients, but you get the idea.

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So I'm going to save that change in models that pay in order to register these changes for the ST method.

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I do need to restart my shell again.

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Otherwise it hasn't actually registered the changes to the patient class you imported.

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So what I'm going to say is, again, Python, after you've quit out of the other shells, remember

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to quit out of the shell is simply quit open close parentheses.

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But now I'm going to restart it with Python managed the pie shell.

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There we go.

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And so let's import again from.

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Office, not models.

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In poor patient.

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And then we're going to say again, patients, the objects.

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All enter and not your see, your query is a lot different, says Smith Khalil's, 30 years old.

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And again, you could just grab the very first one if you wanted to see something like you have an instance

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from the patient table or a patient model.

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And then Smith Carl is three years old.

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OK, so that is how we can grab everything from a database table or just grab particular instances as

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well as slicing, so you could also slice with index notation.

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So, for example, I can go zero all the way up to, but not including index two.

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And I see a query set with two patients.

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Typically, we don't want to just grab everything and then index off of that.

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Instead, we want to filter and then get particular entries.

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So let's talk about that in the next lecture.