1 00:00:05,190 --> 00:00:10,740 Welcome everyone to this continued discussion of filtering query results in this lecture will focus 2 00:00:10,740 --> 00:00:12,660 on a filter and get methods. 3 00:00:13,820 --> 00:00:19,310 The get operation or method allows us to grab a single item from the model table. 4 00:00:19,670 --> 00:00:24,020 Now this is typically reserved for something where you're pretty sure there's only one single unique 5 00:00:24,020 --> 00:00:24,500 entry. 6 00:00:24,710 --> 00:00:26,690 Otherwise, get actually returns an error. 7 00:00:27,110 --> 00:00:32,509 For example, the default primary key that is automatically created by jingo, such as Piqué, is equal 8 00:00:32,509 --> 00:00:38,180 to one, two, three or any other number, which has a unique index position row in that table. 9 00:00:38,240 --> 00:00:40,430 That's typically what you see get used for. 10 00:00:41,700 --> 00:00:46,950 If we want to further filter our results rather than just grab all or get a single item, we can use 11 00:00:46,950 --> 00:00:51,780 the filter method to narrow down based on conditions and the filter methods can actually be chained 12 00:00:51,780 --> 00:00:52,340 together. 13 00:00:54,010 --> 00:00:59,620 Django also provides operators for query sets, which allows us to actually directly use logic like 14 00:00:59,620 --> 00:01:03,130 an and operator or operator within a single filter call. 15 00:01:03,670 --> 00:01:09,370 So these operators actually need to be imported from Django DB models from the queue function, and 16 00:01:09,370 --> 00:01:10,900 we'll show you how to do that later on. 17 00:01:11,910 --> 00:01:17,430 So what we're going to do is explore the following topics getting a single entry from our table with 18 00:01:17,430 --> 00:01:23,730 the get method filtering down to get maybe a set that we're interested in of results and then how to 19 00:01:23,730 --> 00:01:25,830 use operators in conjunction with filters. 20 00:01:26,130 --> 00:01:27,600 Let's head back to our code editor. 21 00:01:28,900 --> 00:01:35,210 OK, so here I am inside Visual Studio code recall that our model technically has three fields or attributes. 22 00:01:35,230 --> 00:01:41,260 The first name, last name and h, but also remember that when we actually ran the initial migration, 23 00:01:41,650 --> 00:01:48,700 jingo automatically creates an I.D. for this model, and the I.D. is a big auto field. 24 00:01:49,240 --> 00:01:55,720 Auto stands for the fact that it's going to automatically increment that number each time you actually 25 00:01:55,720 --> 00:01:57,010 put in a new row. 26 00:01:57,040 --> 00:02:00,310 So it's going to be and then an +1 and +2 and so on. 27 00:02:00,310 --> 00:02:05,710 So it starts at the number one, then two, the three, then four, etc. Big just means it allows it 28 00:02:05,710 --> 00:02:11,140 to be a very large integer because jingo technically doesn't know how many entries are going to put. 29 00:02:11,380 --> 00:02:14,350 So it allows us to be a very large integer number. 30 00:02:15,100 --> 00:02:21,040 That means every time you actually put in a new data entry row into your table, there's going to be 31 00:02:21,070 --> 00:02:23,950 a primary key or ID associated with it. 32 00:02:24,250 --> 00:02:31,180 And the primary key is equal to true is what's associating the fact that this ID column or index is 33 00:02:31,180 --> 00:02:32,950 actually the primary key as well. 34 00:02:33,430 --> 00:02:39,040 This is super useful because now you have a unique identifier for each entry in your data table. 35 00:02:39,050 --> 00:02:44,410 That means even if you have a patient with the same first name and same last name and same age as someone 36 00:02:44,410 --> 00:02:50,050 else like Mike Smith age 30 and you happen to have two patients with that, you can uniquely identify 37 00:02:50,050 --> 00:02:51,580 them by their I.D.. 38 00:02:52,030 --> 00:02:57,820 You can think about this in the same way as your driver's license has a unique ID number or your medical 39 00:02:57,820 --> 00:03:00,070 insurance card or your Citizen's ID. 40 00:03:00,490 --> 00:03:05,410 All have unique ID numbers that we don't get confused if you happen to share the same first name, last 41 00:03:05,410 --> 00:03:07,330 name and birthday as someone else. 42 00:03:07,810 --> 00:03:14,680 OK, so the fact that we know I.D. is a unique identifier then allows us to use get. 43 00:03:14,980 --> 00:03:24,220 So we're going to do here is, say, patients that objects that get and then I can say piqué or primary 44 00:03:24,220 --> 00:03:27,100 key and then set the sequel to something like one. 45 00:03:27,670 --> 00:03:33,510 Keep in mind in sequel, the indexing starts at one, not zero, like in Python. 46 00:03:33,520 --> 00:03:39,850 So if I want the very first item that I ever entered, I would say Piqué is equal to one, and then 47 00:03:39,850 --> 00:03:41,170 I would get back my patient. 48 00:03:41,170 --> 00:03:43,660 Smith or Carl Smith is three years old. 49 00:03:43,990 --> 00:03:47,800 Remember, Carl Smith was the very first patient I put into this table. 50 00:03:48,520 --> 00:03:55,930 You should also note that it is only designed to grab the single item that can be retrieved, and it's 51 00:03:55,930 --> 00:04:01,090 actually going to report back an error if you try to grab more than one item, and we'll show more on 52 00:04:01,090 --> 00:04:01,650 that later. 53 00:04:01,660 --> 00:04:06,720 For example, maybe I say patient objects doc get in. 54 00:04:06,850 --> 00:04:14,110 Imagine I tried to put some sort of filter in this like first name equal to Smith because I know there's 55 00:04:14,110 --> 00:04:15,010 more than one there. 56 00:04:15,280 --> 00:04:19,209 If I try to do something like this, this is going to give you an error and it's going to say, Hey, 57 00:04:19,209 --> 00:04:20,140 that doesn't exist. 58 00:04:20,140 --> 00:04:23,550 And the fact that there is no first name was Smith. 59 00:04:23,560 --> 00:04:24,720 That's one possible error. 60 00:04:24,760 --> 00:04:26,050 This patient just doesn't exist. 61 00:04:26,410 --> 00:04:29,440 Another possible error is if I say last name Smith. 62 00:04:30,940 --> 00:04:35,680 So note here, I'm saying last name Smith, which I know is actually something in my database. 63 00:04:36,280 --> 00:04:37,990 Then I get back another error. 64 00:04:38,080 --> 00:04:39,550 Multiple objects return. 65 00:04:39,670 --> 00:04:40,540 And this is key. 66 00:04:40,750 --> 00:04:47,620 The get method can only return a single object, and that's specifically designed to make sure when 67 00:04:47,620 --> 00:04:53,800 you're using get, you should be using it in a place where you only expect a single patient or a single 68 00:04:53,800 --> 00:04:56,310 data row to be returned, something like primary key. 69 00:04:56,800 --> 00:05:02,350 And it actually has a really nice error Message says, Hey, this returned more than one patient and 70 00:05:02,350 --> 00:05:03,640 it actually says an irritant. 71 00:05:03,670 --> 00:05:04,030 Three. 72 00:05:04,450 --> 00:05:09,520 So this is basically telling you you should probably be using all again with some sort of filter attached 73 00:05:09,520 --> 00:05:09,790 to it. 74 00:05:10,300 --> 00:05:15,590 So let's talk about filters because you are not going to typically be running a filter like this. 75 00:05:15,610 --> 00:05:17,860 Instead, you actually do a filter call. 76 00:05:18,070 --> 00:05:19,120 So we do the following. 77 00:05:19,450 --> 00:05:26,290 Let me clear this I'm going to say patient the objects and then I call a filter. 78 00:05:27,010 --> 00:05:33,430 And inside this filter is where I can begin to do things like Boolean statements, so I can say something 79 00:05:33,430 --> 00:05:36,100 like, OK, filter, where the last name? 80 00:05:37,200 --> 00:05:38,340 Is equal to Smith. 81 00:05:38,370 --> 00:05:40,050 Notice I'm doing all lowercase Smith here. 82 00:05:41,160 --> 00:05:44,670 And you're going to have match access to whatever data entries you put in as well. 83 00:05:45,090 --> 00:05:50,070 So then instead of saying get because that's for a single item, I can say. 84 00:05:51,000 --> 00:05:56,550 All I enter, and now I get back to query sit where all their last names happen to be Smith. 85 00:05:57,480 --> 00:05:59,820 I can also chain filters together. 86 00:06:00,180 --> 00:06:04,320 So let's say I wanted to wear the last name is Smith, and they happened to be 40 years old. 87 00:06:04,680 --> 00:06:09,720 I could do the same command as before, but now I can actually call Filter on top of that again. 88 00:06:10,200 --> 00:06:16,040 So I can say filter, where let's say age is equal to 40. 89 00:06:16,740 --> 00:06:17,880 And then I can call all. 90 00:06:19,480 --> 00:06:22,840 And now I get the further refined query set. 91 00:06:23,140 --> 00:06:28,540 And what's nice about this is this technically means you can assign this query set to a variable and 92 00:06:28,540 --> 00:06:31,960 then call dot filter on that particular variable. 93 00:06:32,290 --> 00:06:36,460 It's kind of up to you, depending on how you're actually organizing your views and templates and structures 94 00:06:36,460 --> 00:06:39,580 with models on how exactly you're going to end up filtering things. 95 00:06:40,030 --> 00:06:42,370 The other point I want to make here make clear this. 96 00:06:44,250 --> 00:06:49,560 And now let's talk about operators within a query set in order to use this. 97 00:06:49,860 --> 00:06:55,720 We have to import what's known as a queue object inside of Django as a quick note. 98 00:06:55,740 --> 00:06:57,930 You should definitely check out the documentation on this. 99 00:06:57,960 --> 00:07:03,690 It's kind of this weird beast, but once you get used to it, it allows you to have a lot more functionality 100 00:07:03,960 --> 00:07:07,200 that is more skill based in order to filter out results. 101 00:07:07,530 --> 00:07:13,950 So this is going to allow us to add an end or conditions and meaning I want both conditions to be true 102 00:07:14,100 --> 00:07:14,820 or meaning. 103 00:07:14,820 --> 00:07:17,670 I will either condition to be true in order to use. 104 00:07:17,670 --> 00:07:19,350 This will have to say from. 105 00:07:20,500 --> 00:07:25,930 Django, the D B, the model's import and then just capital Q. 106 00:07:26,840 --> 00:07:27,120 OK. 107 00:07:27,140 --> 00:07:29,910 And this is known as a Q object within Django. 108 00:07:29,930 --> 00:07:34,580 So if you're ever wondering where the documentation is, you can just Google search Q objects within 109 00:07:34,580 --> 00:07:35,030 Django. 110 00:07:35,240 --> 00:07:37,250 And it's a Q object class. 111 00:07:37,370 --> 00:07:42,940 Now again, this essentially allows you to use or and and operations later on work. 112 00:07:42,980 --> 00:07:46,570 Discuss even more complex lookups with field lookup objects. 113 00:07:46,580 --> 00:07:53,690 But right now we're just discussing or in and operations sort of come back here and let's imagine I 114 00:07:53,690 --> 00:08:00,950 want people that are both have a last name of Smith and have an age greater than 30. 115 00:08:01,010 --> 00:08:06,890 I could use to filter calls for this, but now that I have the queue operator, I can actually put this 116 00:08:06,890 --> 00:08:08,750 within a single filter call. 117 00:08:09,260 --> 00:08:15,530 So we're going to say patient the objects that and then we're going to say, is filter. 118 00:08:16,250 --> 00:08:20,200 And inside this filter is where I can begin to use my Q statements. 119 00:08:20,210 --> 00:08:26,660 So instead of stacking two filters, I'm going to say Q, and this is a function that takes in a condition 120 00:08:26,660 --> 00:08:30,230 like something like name is equal to Smith. 121 00:08:30,680 --> 00:08:34,370 Keep in mind, these conditions do need to be in equal condition. 122 00:08:34,669 --> 00:08:38,059 Later on, we're going to discuss how to do something like less than or greater then. 123 00:08:38,070 --> 00:08:39,620 So keep that in mind right now. 124 00:08:40,190 --> 00:08:45,860 And if you want to keep stacking these, you have to use a pipe operator for or in an ampersand for. 125 00:08:45,860 --> 00:08:51,970 In so case, you're not familiar if those again, it's this symbol for or sort of pipe operator and 126 00:08:51,980 --> 00:08:53,570 an ampersand for end. 127 00:08:53,750 --> 00:08:55,640 So let's use an ampersand for right now. 128 00:08:56,150 --> 00:09:01,100 So I'm going to say ampersand typically shift seven or keyboard, and we're going to say, all right, 129 00:09:01,100 --> 00:09:02,900 I'll want the last name equal to Smith. 130 00:09:02,900 --> 00:09:07,130 And then we add another queue operator condition or queue object look up. 131 00:09:07,700 --> 00:09:10,520 So we're going to say Q and let's say H. 132 00:09:11,520 --> 00:09:13,950 There has to be equal to 40. 133 00:09:16,800 --> 00:09:18,930 OK, so I want both those conditions to be true. 134 00:09:19,290 --> 00:09:23,190 Notice we've technically already done something like this, but we did it with two filter calls. 135 00:09:23,610 --> 00:09:29,460 Now I'm doing one filter call with the use of a queue object, and then we're going to say, grab me 136 00:09:29,880 --> 00:09:31,570 everything that meets those conditions. 137 00:09:31,590 --> 00:09:33,000 You run that and I get back. 138 00:09:33,270 --> 00:09:36,720 Susan Smith, who's 40 years old, and Adam Smith, who's also 40 years old. 139 00:09:37,170 --> 00:09:41,610 So that is the queue operator, which allows for complex lookups. 140 00:09:41,940 --> 00:09:47,400 Keep this in mind because we're going to add queue operators with field lookups, which are even more 141 00:09:47,400 --> 00:09:48,720 complex later on. 142 00:09:49,140 --> 00:09:53,790 So so far, we've covered the ability to use get, which is for grabbing a single item. 143 00:09:54,150 --> 00:09:57,570 We almost always use primary key with that because we expect a single item. 144 00:09:57,960 --> 00:10:03,290 We've also learned how to filter based off conditions like, I want this attribute equal to this. 145 00:10:03,300 --> 00:10:07,950 I want another attribute equal to that, and I can keep stacking those and then use all at the end to 146 00:10:07,950 --> 00:10:08,780 grab everything. 147 00:10:09,210 --> 00:10:16,680 Or I could also use this queue operator in order to put and or operations within my filter call. 148 00:10:17,040 --> 00:10:23,580 So if I wanted to do last name is equal to Smith or ages 40, I could come back here and delete the 149 00:10:23,580 --> 00:10:25,800 ampersand and put in a pipe operator. 150 00:10:26,190 --> 00:10:30,780 That's essentially saying, give me all the entries that have the last name Smith or have an age of 151 00:10:30,780 --> 00:10:31,530 40 years old. 152 00:10:31,950 --> 00:10:37,200 Notice now I also get something like Carl Smith, who is 30 years old, but he also has the last name 153 00:10:37,200 --> 00:10:37,560 Smith. 154 00:10:38,100 --> 00:10:45,690 OK, so now we're going to do in the next lecture, expand our understanding of filtering with a very 155 00:10:45,690 --> 00:10:48,270 powerful tool called field lookups. 156 00:10:48,480 --> 00:10:49,440 I'll see you in the next lecture.