WEBVTT 00:07.850 --> 00:10.730 I will call you back again to another video lecture and mic call. 00:10.730 --> 00:15.830 And in this video lecture is called Head and Lane but not no constraint. 00:16.370 --> 00:20.300 Alright, so the previous lecture I was able to teach you about a unique constraint and we can see how 00:20.300 --> 00:21.290 that played out. 00:21.290 --> 00:23.600 And I hope you practice that. 00:23.600 --> 00:28.670 And let's go ahead and learn about another constraint known as not null constraint. 00:28.880 --> 00:33.560 And let's go ahead and say the previous table we created, which is employee table I is no longer a 00:33.560 --> 00:35.150 variable because I've dropped the table. 00:35.180 --> 00:37.430 Now let's go ahead and recreate that exact table. 00:37.430 --> 00:42.620 So instead of wasting our time typing this one by one, let's go ahead and put the table back in here. 00:42.620 --> 00:45.380 And that is the table that we have in the previous lecture. 00:45.380 --> 00:47.420 And that contains the unique constraint. 00:47.450 --> 00:49.910 So go ahead and remove the unique constraint right now. 00:50.150 --> 00:58.520 So if I want to add a not null constraint maybe I would add that to salary or first name or employee. 00:58.550 --> 01:04.210 What I need to do is that I'll go over to salary and I'll go ahead and add not not. 01:04.210 --> 01:08.020 So this salary will never, ever be known. 01:08.050 --> 01:08.710 All right. 01:08.710 --> 01:10.510 So that is what I'm going to do. 01:10.540 --> 01:15.370 You can add that to first name or to employee ID or any other column you've just created. 01:15.400 --> 01:18.850 Now let's go ahead and create this table by putting all this. 01:18.850 --> 01:21.130 So down here you can see I've created this table. 01:21.160 --> 01:21.670 All right. 01:21.700 --> 01:25.180 Now let's go ahead and view the table we just created. 01:25.180 --> 01:36.580 So go ahead and say select all from employees can apply semicolon at the end. 01:36.610 --> 01:38.200 And go ahead and hit on this. 01:38.200 --> 01:42.400 And this is where we have employee ID first name and salary. 01:42.430 --> 01:44.350 Now we've just created this. 01:44.350 --> 01:47.680 And now what if like we have the students table. 01:47.710 --> 01:48.760 Go ahead and refresh this. 01:48.790 --> 01:50.500 We have the previous table right in here. 01:50.500 --> 01:56.650 So the students table right now if you want to do that let me go ahead and show you using the employees 01:56.650 --> 01:57.310 table. 01:57.340 --> 01:58.810 Go ahead and remove this. 01:58.810 --> 02:02.180 And let's go ahead and insert some data right in here. 02:02.180 --> 02:05.810 So the previously we created some data and that is it right in here. 02:05.810 --> 02:08.630 So tables employees and that is employee ID. 02:08.780 --> 02:10.730 And this is what we have. 02:10.760 --> 02:12.020 This is the table created. 02:12.050 --> 02:16.160 Now I want to enter some data which is the previous data we created. 02:16.190 --> 02:18.050 Go ahead and put that back. 02:18.050 --> 02:22.220 So I have this data set for you Will because I'm going to download that from the resource folder. 02:22.310 --> 02:25.250 Go ahead and download that and that it is right in there. 02:25.250 --> 02:27.320 So this is the data we have. 02:27.320 --> 02:32.570 And I want to insert this data right in here and have inserted that data. 02:32.600 --> 02:37.550 Let's go ahead and select all from. 02:39.860 --> 02:43.490 Employees put a semicolon at the end and let's go ahead and check it out. 02:43.490 --> 02:45.650 So now we can see that right in here. 02:45.710 --> 02:48.890 Go ahead and bring this down so you can see everything. 02:48.890 --> 02:51.260 So we have this data. 02:51.260 --> 02:54.320 And I want to apply the not null. 02:54.350 --> 02:56.480 Maybe I want to add that to salary. 02:56.510 --> 03:01.000 What I need to do is I go warhead and or Tardis. 03:01.690 --> 03:03.520 Uh, table. 03:03.520 --> 03:10.480 So what I need to go ahead and do is that I gotta say alter table, then give the name of the table, 03:10.480 --> 03:12.340 and that is employees. 03:12.490 --> 03:17.200 And, uh, I'll go ahead and say modify. 03:17.410 --> 03:17.950 All right. 03:17.950 --> 03:18.970 So modify. 03:19.000 --> 03:23.800 Remember that I did not know and I can add that to salary. 03:23.830 --> 03:25.810 So I'm going to say salary. 03:25.810 --> 03:34.270 And uh that is int and not know the semicolon at the end. 03:34.270 --> 03:36.580 And let's go ahead and execute this query. 03:36.610 --> 03:44.800 Now let's go ahead and check out and see you can see that uh employees modify salary has been added 03:44.800 --> 03:45.520 not known. 03:45.520 --> 03:49.210 And that is what we have with the previously okay. 03:49.240 --> 03:53.890 Now that is a way you can do that for a table that hasn't existed. 03:53.890 --> 03:55.810 And you have added some data right in there. 03:55.840 --> 04:02.720 Now let's go ahead and check if this actually works by updating or inserting a new data. 04:02.750 --> 04:03.980 This guy had to remove this. 04:03.980 --> 04:11.750 I'll go ahead and insert a new insert into employee. 04:13.880 --> 04:15.650 So insert into employees. 04:15.650 --> 04:17.450 Let's go ahead and add the value. 04:17.480 --> 04:19.310 Go ahead and add values. 04:19.730 --> 04:26.510 And I'm going to add the very first one because we have the next id is five. 04:26.510 --> 04:31.160 And let's the name be mirrored. 04:31.190 --> 04:31.790 Oh wow. 04:31.790 --> 04:34.220 That is mirror. 04:34.250 --> 04:37.280 All right so and the mirror I'm going to add it to be. 04:37.280 --> 04:39.860 No I remember I made this array not to be. 04:39.860 --> 04:40.250 No. 04:40.280 --> 04:40.730 All right. 04:40.730 --> 04:42.770 So I believe comma at the end. 04:42.860 --> 04:45.710 And drag this up so it can be good to see that. 04:45.710 --> 04:47.630 And I go ahead and run this. 04:47.630 --> 04:50.210 And now here you can see you have an error. 04:50.240 --> 04:54.080 You cannot have an you have an error in your SQL syntax. 04:54.110 --> 04:54.620 Okay. 04:54.650 --> 04:59.080 So let's go ahead and it says Murano. 04:59.080 --> 05:00.880 And that is not possible. 05:00.880 --> 05:01.990 So why? 05:02.740 --> 05:05.140 Because I'm getting a different error right in the air. 05:05.380 --> 05:07.990 Go ahead and check out this again. 05:07.990 --> 05:11.830 And it says quorum salary cannot be known. 05:11.860 --> 05:17.620 So you can see that you cannot be know because the first error shows that there is no comma right in 05:17.620 --> 05:17.890 here. 05:17.920 --> 05:22.870 It says that my SQL, uh syntax has an error. 05:22.900 --> 05:25.300 That is why I knew that I didn't put a comma. 05:25.330 --> 05:26.440 I want to add a comma. 05:26.470 --> 05:31.750 I try to execute the query and it says salary cannot be null. 05:32.410 --> 05:33.640 So you can see that. 05:33.640 --> 05:38.080 And let's go ahead and select these. 05:38.620 --> 05:44.200 So if I go ahead and select this we'll go ahead and see what we have right in there. 05:44.710 --> 05:48.400 Select all from. 05:52.150 --> 05:55.030 Employees and go ahead and run this. 05:55.060 --> 05:56.050 Let's check it out. 05:56.410 --> 05:59.030 So because of the not knowing, we're not getting anything. 05:59.030 --> 06:02.120 And the only way to do this, maybe I don't want to add anything. 06:02.120 --> 06:04.280 I can go ahead and put a zero right in there. 06:04.280 --> 06:06.680 And now let's go ahead and run this and check it out. 06:07.010 --> 06:08.090 Go ahead and drag this. 06:08.120 --> 06:10.850 You can see that our code has executed successfully. 06:11.000 --> 06:13.280 Go ahead and drag this down. 06:13.850 --> 06:16.760 And I want to drag this up so I can be able to see our table. 06:17.210 --> 06:19.280 And I can see me around is zero. 06:19.280 --> 06:22.070 But Mira can never be null. 06:22.400 --> 06:27.950 So there is a way we use a null, not null constraint in MySQL. 06:27.950 --> 06:29.630 So go ahead and check it out. 06:29.660 --> 06:30.440 Practice with it. 06:30.440 --> 06:33.260 You can add to an F-16 data. 06:33.560 --> 06:36.740 You can also add it when you're inserting a new data into your table. 06:36.740 --> 06:38.450 So go ahead and practice with it. 06:38.450 --> 06:42.380 And when you're updating you can also also check it out. 06:42.380 --> 06:43.640 So thank you so much. 06:43.640 --> 06:46.490 And I'm going to see you in the next video lecture.