WEBVTT 00:00.150 --> 00:04.770 So we're moving onto the R of crud which is read. 00:04.860 --> 00:08.430 How do we retrieve and search data from a database. 00:08.760 --> 00:13.460 And we've actually already seen this the magic command is select. 00:13.950 --> 00:19.080 So remember when we were doing this earlier select a star from cats I told you not to worry about it 00:19.080 --> 00:24.060 too much because we'd spend more time on it and it was really just something that we needed to have 00:24.600 --> 00:30.150 to check our work at the at that time when we were inserting data but we didn't actually talk about 00:30.150 --> 00:32.000 how it works what the star means. 00:32.460 --> 00:33.910 That's what we're going to do now. 00:34.320 --> 00:42.540 So the star in select star from cats me and give me all the columns in the cats table. 00:42.540 --> 00:45.790 So we're asking for the cats table. 00:45.840 --> 00:47.200 That's the from cats. 00:47.490 --> 00:50.840 And in that table we just want everything that we have. 00:50.940 --> 00:57.890 So in our case that means cat Heidi name age and breed we want all of them coming back to us. 00:57.960 --> 01:00.140 So let's do that now. 01:00.300 --> 01:05.320 Select a star from cats. 01:05.970 --> 01:10.380 You can see we get cat ID name breed and age. 01:10.770 --> 01:13.530 And we also get every single cat. 01:13.560 --> 01:14.510 No one is missing. 01:14.550 --> 01:16.700 These are the seven that we inserted. 01:16.770 --> 01:22.540 So that's the basics of select star which you'll use often just to check things out. 01:22.650 --> 01:28.410 But we can also get more specific about what data we want back which is where the select expression 01:28.410 --> 01:29.270 comes in. 01:29.700 --> 01:36.000 Basically there's a way for us to specify what columns we want in particular I only want the ID or I 01:36.000 --> 01:40.220 only want cats names and age but not the breed. 01:40.230 --> 01:48.420 So to do that rather than saying select star we can do things like select name from cats and if we do 01:48.420 --> 01:54.570 that select name from cats What do you think the table will look like. 01:55.920 --> 01:56.750 Looks like this. 01:56.750 --> 02:02.720 We only get name so it gives us all seven names but nothing else. 02:03.410 --> 02:07.480 We could also do select age from cats. 02:12.590 --> 02:14.420 And hopefully this is what you expected. 02:14.420 --> 02:21.830 We just get a bunch of ages and just to hammer it home here we can also do a select let's do cat ID 02:22.070 --> 02:28.480 from cats and we get one two three four five six seven. 02:28.880 --> 02:29.420 OK. 02:29.720 --> 02:36.290 So that's useful enough but oftentimes we want more than one piece of data but we don't want everything. 02:36.830 --> 02:39.420 And that's where this comma separated post comes in. 02:39.440 --> 02:47.170 So this whole thing is the select expression where saying select name and age from cat so we can try 02:47.170 --> 02:47.320 it. 02:47.310 --> 02:53.630 Now select name comma age from cats. 02:53.800 --> 02:55.580 And what do you think we'll see. 02:56.470 --> 03:00.680 So we get a table with name and age returned back. 03:00.850 --> 03:06.620 So there's no limit on that we could do name age comma cat ID common breed which would be the same thing. 03:06.630 --> 03:13.630 So like star we could do name age and breed or cat ID and name and age and so on I think you get it. 03:13.630 --> 03:16.310 We can mix and match whatever fields we want back. 03:16.690 --> 03:24.670 So just to illustrate my point let's do a select cat Heidi common name comma age from cats and we hit 03:24.670 --> 03:27.360 enter and we get those three fields. 03:27.640 --> 03:32.310 Notice we're missing breed but we could just go at that and if we wanted 03:35.260 --> 03:37.380 and noticed that the order matters. 03:37.480 --> 03:41.040 So I said can I do the name then age then breed. 03:41.290 --> 03:42.690 And that's what we get. 03:42.820 --> 03:44.500 But if I just did a select star 03:47.550 --> 03:53.080 it uses the default order which is cat ID name breed and then age which is just how we entered it when 03:53.080 --> 03:59.650 we created the table so we could reverse it if I wanted to I select age then breed then name it then 03:59.650 --> 04:03.850 Cat ID from cats. 04:04.150 --> 04:05.320 And there we go. 04:05.750 --> 04:06.030 OK. 04:06.040 --> 04:11.380 So that's pretty much all there is to this select expression for now at least where we're just specifying 04:11.410 --> 04:16.930 exactly which columns we want or we can default and use the star which will give us all columns.