WEBVTT 1 00:00:00.290 --> 00:00:01.620 Hi guys and welcome back. 2 00:00:01.620 --> 00:00:03.070 In this video we're going to learn 3 00:00:03.070 --> 00:00:05.990 how to delete rows from a database 4 00:00:05.990 --> 00:00:08.860 and we're also going to implement this in our app. 5 00:00:08.860 --> 00:00:11.010 So Delete From looks like this, 6 00:00:11.010 --> 00:00:15.520 we've got "Delete from users where surname equal Smith." 7 00:00:15.520 --> 00:00:17.150 So the first part tells the database 8 00:00:17.150 --> 00:00:19.940 that we want to delete rows from the user's table, 9 00:00:19.940 --> 00:00:22.540 by default that's going to delete everything. 10 00:00:22.540 --> 00:00:25.020 So this second part here, the Where clause, 11 00:00:25.020 --> 00:00:27.710 filters them so that we only delete 12 00:00:27.710 --> 00:00:30.250 the rows that match this clause. 13 00:00:30.250 --> 00:00:31.790 Otherwise it's going to delete everything. 14 00:00:31.790 --> 00:00:33.400 Seriously important. 15 00:00:33.400 --> 00:00:36.800 Remember the Where clause, just as we did with the update, 16 00:00:36.800 --> 00:00:38.760 otherwise everything's going to be deleted, 17 00:00:38.760 --> 00:00:41.350 and you'll get to keep the table but none of the contents. 18 00:00:41.350 --> 00:00:42.940 So that's pretty important. 19 00:00:42.940 --> 00:00:44.410 Don't forget about that. 20 00:00:44.410 --> 00:00:46.440 Let's go into our code editor 21 00:00:46.440 --> 00:00:49.373 and work on deleting rows from our table. 22 00:00:50.540 --> 00:00:53.350 All right, so what we're going to do is create our Query, 23 00:00:53.350 --> 00:00:55.690 that takes care of deleting movies. 24 00:00:55.690 --> 00:00:57.967 And as you know, it's really straight forward, 25 00:00:57.967 --> 00:01:02.967 "Delete movie" for example can be " Delete from movies". 26 00:01:03.130 --> 00:01:04.390 And here we're telling SQL 27 00:01:04.390 --> 00:01:07.384 that we want to delete something from the movies table. 28 00:01:07.384 --> 00:01:11.770 And we wanna do "Where title equal question mark" 29 00:01:11.770 --> 00:01:13.390 and that means that in the function 30 00:01:13.390 --> 00:01:16.730 we are going to pass in the argument with the titles 31 00:01:16.730 --> 00:01:19.320 that we want to delete from the table. 32 00:01:19.320 --> 00:01:22.810 We're going to be re-implementing this file for stage two 33 00:01:22.810 --> 00:01:24.550 in the next video but I wanted to show you 34 00:01:24.550 --> 00:01:27.270 how this works in DB Browser as well, 35 00:01:27.270 --> 00:01:29.410 so let's go over to that. 36 00:01:29.410 --> 00:01:31.050 So here I've opened DB Browser. 37 00:01:31.050 --> 00:01:32.500 If I go to Browse Data, 38 00:01:32.500 --> 00:01:35.500 you can see that I've got "The Matrix" here. 39 00:01:35.500 --> 00:01:37.820 And if we go to the Execute SQL tab, 40 00:01:37.820 --> 00:01:40.744 we can do "Delete from movies". 41 00:01:40.744 --> 00:01:42.430 Remember if we just run this, 42 00:01:42.430 --> 00:01:45.020 that's gonna delete everything from the movie's table. 43 00:01:45.020 --> 00:01:47.224 At the moment we only have one row so it's not a big deal 44 00:01:47.224 --> 00:01:50.810 but we always want to include a Where clause. 45 00:01:50.810 --> 00:01:54.130 So we'll do "Delete from movies where title equal" 46 00:01:54.130 --> 00:01:56.970 And now we pass in the string inside quotation marks, 47 00:01:56.970 --> 00:02:00.230 single quotation marks, and that's "The Matrix" 48 00:02:00.230 --> 00:02:02.660 And now we can run this, 49 00:02:02.660 --> 00:02:05.300 and you can see that get "Query executed successfully." 50 00:02:05.300 --> 00:02:07.624 We go back to Browse Data, the movie's gone. 51 00:02:07.624 --> 00:02:09.515 All right, thank you guys for watching this video. 52 00:02:09.515 --> 00:02:11.480 We're going to go into the next one 53 00:02:11.480 --> 00:02:13.822 and re-implement the database.py file. 54 00:02:13.822 --> 00:02:15.053 I'll see you there.