WEBVTT 00:01.620 --> 00:02.220 Okay. 00:02.220 --> 00:06.540 Let's talk about the migrations in this video. 00:06.570 --> 00:13.950 So what migrations are if we come back to the run server, you can see here, if I'll make a more space 00:13.950 --> 00:21.600 here, you can see whenever I run the server and that was the command I run with the manage by clicking 00:21.600 --> 00:22.740 on the button here. 00:22.740 --> 00:28.620 And then we have some information here you have 17 unapplied migrations. 00:28.620 --> 00:30.300 So what does it mean? 00:30.330 --> 00:32.100 Unapplied migration? 00:32.310 --> 00:40.200 It means that we have some data in our project and application that hasn't been applied to our database 00:40.200 --> 00:40.770 yet. 00:40.770 --> 00:49.020 So in order to make the to set up our database with the new data we have, it's not new data, it's 00:49.020 --> 00:53.310 new schema we have and would like to keep it in our application. 00:53.310 --> 00:55.560 We need to do a migrate. 00:55.560 --> 01:01.850 So here we have the comment we need to run our migration, migrate means. 01:01.920 --> 01:05.340 So I'll copy this and I will go to the terminal. 01:05.340 --> 01:09.120 Inside here I'm inside virtual Environment inside tutorial. 01:09.120 --> 01:12.390 So what I can do is I can paste this. 01:12.390 --> 01:22.410 So basically we have I need to use Python3 Manage.py the same way as we use it and then migrate. 01:22.410 --> 01:29.220 That means we'll apply the current migrations that will be applied from the project, the default that 01:29.220 --> 01:34.680 Django created for us, and it will create that schema on the database. 01:34.680 --> 01:43.380 At this point we have database SQLite here, so if I will click Enter, you can see here that that many 01:43.380 --> 01:50.850 changes has been applied for our migration, for our database and from where this is coming from if 01:50.850 --> 01:52.140 we go to our. 01:54.940 --> 01:58.450 Project, which is first, and then we open the settings. 02:00.790 --> 02:09.370 We'll scroll here and we can see see installed apps In that section, we tell Django what kind of application 02:09.370 --> 02:11.890 we'd like to use within our project. 02:11.890 --> 02:14.350 And we have, for example, here admin. 02:14.350 --> 02:21.850 And if we go here, you can see that some of these migrations let me. 02:22.590 --> 02:23.700 Find it here. 02:23.700 --> 02:25.670 So we have admin, this one. 02:25.680 --> 02:31.650 So we have migration from this application applied to our database. 02:31.680 --> 02:36.390 You have also out here and then you have out here. 02:36.390 --> 02:44.550 So each of this application has a migration files that we can use to apply to our database. 02:44.550 --> 02:49.590 And you can see we have a few of them and basically they are all coming from here. 02:49.590 --> 02:55.860 So that's like an application has been added automatically to our project and we can use it straight 02:55.860 --> 02:56.340 away. 02:56.340 --> 03:02.790 So the admin section I've showed you before, it's coming from here, but in order to use it you need 03:02.790 --> 03:04.170 to do a migration. 03:04.170 --> 03:08.460 So we applied all migrations from this installed apps. 03:08.520 --> 03:14.490 Okay, but inside our application demo we also have folder migrations. 03:14.490 --> 03:15.780 If I will open here. 03:15.780 --> 03:19.530 We don't have any files here except of init. 03:19.560 --> 03:27.780 That means this init is just a initiate some command, so it's not something that we might be interested 03:27.780 --> 03:30.810 in and we can consider this folder as empty. 03:31.050 --> 03:31.410 Okay. 03:31.410 --> 03:39.480 So what we can do if I go to the models here and that's demo models in this, as I said before, in 03:39.480 --> 03:40.020 this. 03:40.800 --> 03:43.740 File will create our models. 03:44.160 --> 03:45.930 If we create our model here. 03:46.080 --> 03:53.280 Here it will be basically kind of creating some kind of container or a class that we can store some 03:53.280 --> 03:55.130 information in our database. 03:55.140 --> 03:59.270 And I will show you how to create a class based models. 03:59.280 --> 04:03.420 So basically what we need to do is we need to create a class. 04:05.310 --> 04:07.020 And then we name that class. 04:07.020 --> 04:15.720 Let's say it's gonna be a book, and that is Capital B, But by convention, we name our classes with 04:15.720 --> 04:24.800 capital letters so we can do book here, and then we can use some built in Django functionality. 04:24.810 --> 04:33.090 So inside here I will do models and then I will do model models. 04:33.090 --> 04:37.320 Is that what we import at the top of this file? 04:37.320 --> 04:41.130 So from the models I import model, I will add it to my book. 04:41.130 --> 04:44.190 So inside book I can use it. 04:44.190 --> 04:49.140 So if we have proper indentation here, we can add some fields into the book. 04:49.140 --> 04:57.480 Let's say we would like to have title and then I will explain more about the different types and that 04:57.480 --> 04:59.070 we have available here. 04:59.070 --> 05:02.400 But at the moment I would like to show you how the migrations work. 05:02.400 --> 05:05.280 So model models. 05:07.660 --> 05:08.590 Charfield. 05:12.110 --> 05:12.920 Max length. 05:12.950 --> 05:15.590 For example, we can have it. 05:15.890 --> 05:17.090 36. 05:17.270 --> 05:27.800 So what I did here is I've created a new object and that object will be stored in our database. 05:27.800 --> 05:31.310 And then this object will have a title for the moment. 05:31.310 --> 05:38.060 And we for this title, we'd like to keep it as a char field, which is a simple text, a string, and 05:38.060 --> 05:41.060 we can say Max, length of this will be 36. 05:41.300 --> 05:43.190 Okay, so what's happening now? 05:43.190 --> 05:53.630 If I will go right now to the to our terminal and I will try to run this manage.py migrate again. 05:54.850 --> 06:00.580 It's not going to do anything because we already applied our migrations to our database. 06:00.580 --> 06:01.960 But this is new. 06:01.960 --> 06:08.230 So what we will need to do actually is we need to take whatever changes we have in this models file. 06:08.230 --> 06:14.050 We need to create migrations and then that migrations will create a new file in this. 06:14.050 --> 06:20.380 And then using command migrate, we can actually apply this migration files into our database. 06:20.620 --> 06:21.760 Okay, let's do that. 06:21.760 --> 06:23.980 And I will also show you how this is. 06:24.220 --> 06:29.110 It's not going to work and I will explain you what we need to do to make it work. 06:29.110 --> 06:36.910 So Python three manage pi the same as we used before and then space. 06:36.910 --> 06:44.260 And then we will use a command, create migrations capital s at demo at the end. 06:44.260 --> 06:46.330 So manage.py create migrations. 06:46.330 --> 06:50.380 That command here will take all the changes here. 06:50.380 --> 06:56.450 So whatever you will add new or change anything here and it will create a file for you. 06:56.450 --> 07:01.070 And we should expect migrations file created in this migration folder. 07:01.070 --> 07:02.870 So try to run it now. 07:03.440 --> 07:10.520 And you can see here and I made a mistake because it's not create migrations, it's make migrations. 07:10.610 --> 07:17.600 So I will do make migrations sorry for a mistake and then make migrations. 07:17.900 --> 07:19.520 No changes detected. 07:19.520 --> 07:21.890 So why this is happening? 07:21.890 --> 07:26.050 We are we have our changes here, but not it has been detected. 07:26.060 --> 07:31.310 The reason for this is we need to go to the settings and inside installed apps. 07:31.310 --> 07:34.190 We need to add our app manually here. 07:34.190 --> 07:36.770 So our application is demo. 07:36.770 --> 07:43.940 So basically what we need to do is at the end of this list, inside the single comma, we can type in 07:43.940 --> 07:46.730 demo that's the name of our application. 07:46.730 --> 07:52.640 And just to be safe, we can put extra comma on the end of this line. 07:52.640 --> 07:55.670 Just if we add another one, there will be no error. 07:55.670 --> 08:02.600 So basically what's happening now is we are telling Django Project that we have our application and 08:02.600 --> 08:04.520 whatever we will have a new application. 08:04.520 --> 08:07.100 We need to add it inside installed apps. 08:07.100 --> 08:11.900 So I'll will save it, save it here and let's make the same command again. 08:11.900 --> 08:17.780 So Python3 Manage.py make migrations and also take a look at the migration folder here. 08:17.780 --> 08:26.780 So if I run it now, you can see here that demo migrations, this file has been created and at the moment 08:26.780 --> 08:27.830 we don't see it here. 08:27.830 --> 08:33.770 But if I will click here, it will appear in a second and you can see here the file is there. 08:33.770 --> 08:41.840 So if I open this file, it's basically a set of rules how to apply our class into our database. 08:41.840 --> 08:48.050 But at this point, this has not been added yet to our database. 08:48.080 --> 08:57.190 The make migrations will only create that file and the 001 initial is the file created with this command. 08:57.190 --> 09:01.060 Make migrations to apply this migrations on the database. 09:01.060 --> 09:02.050 We need to do it. 09:02.050 --> 09:03.220 Migrate again. 09:04.570 --> 09:05.470 Migrate. 09:06.580 --> 09:14.680 And you can see here that demo 001 initial, which is this file has been applied to our database. 09:14.680 --> 09:21.880 And at this point, our changes models, which we have here, are inside our database. 09:21.910 --> 09:28.810 It doesn't mean we have some records in database, but this database is prepared now to have a to store 09:28.810 --> 09:35.650 our books with titles that will be a string up to 36 characters long. 09:35.650 --> 09:38.560 So this is the way you do migrations. 09:38.560 --> 09:44.620 Whatever you will try to store in your database, you will need to go to the models and add it. 09:44.620 --> 09:49.690 So basically you don't need to keep just one field at a time. 09:49.690 --> 09:51.430 You might have more than one. 09:51.430 --> 09:56.720 And if you want to imagine, this will be like a table. 09:56.720 --> 10:03.260 So you have one table for books and then each column will be different field we have. 10:03.260 --> 10:09.860 So for one column you might have a title and then each row will be a record set of record. 10:09.860 --> 10:11.450 Store it in the database. 10:11.870 --> 10:13.070 That's how it works. 10:13.070 --> 10:17.330 And if you would like to have more, then you will add another field here. 10:17.330 --> 10:20.390 And then what you need to do is make migrations. 10:20.390 --> 10:26.360 It will create another file in a migration folder and we'll do that later in the tutorial. 10:26.360 --> 10:34.730 And also once you have that new file, you need to run manage.py migrate and that changes will be applied 10:34.730 --> 10:38.030 to the database in the moment when they will be applied in a database. 10:38.030 --> 10:43.760 You can add and manage the records in the database with that fields.