WEBVTT 00:05.090 --> 00:06.860 I everyone will come back. 00:06.870 --> 00:13.320 So in this video it's going to be the last video that we will be discussing stuff on Mullany. 00:13.440 --> 00:15.600 So should be the last video. 00:15.610 --> 00:17.500 So yeah let's get started. 00:17.520 --> 00:23.490 So updating documents in mongerer Bebe's so Mungo maybe has two functions update and see Mathes and 00:23.490 --> 00:27.150 they're used to update the documents that are already in a college. 00:27.150 --> 00:32.460 So if you already answered that a document into a collection then you can update them were changed and 00:32.460 --> 00:34.940 using the update or the same function. 00:34.950 --> 00:40.860 Now the update method updates the values in the existing document while the Save method replaces the 00:40.860 --> 00:44.370 existing document with the document passed in the Save method. 00:44.370 --> 00:45.180 So what does that mean. 00:45.180 --> 00:52.730 Will the update function basically looks for the records that you want to or that you want to update 00:53.120 --> 00:55.310 and that it doesn't in-place update. 00:55.310 --> 01:00.970 So for example likes where 50 then it would just change this 50 to 100. 01:00.970 --> 01:03.240 For example if you want to change you to a hundred. 01:03.710 --> 01:09.320 But for the save function what it does is it just scraps the whole document creates a new document that 01:09.320 --> 01:11.230 is exactly identical to this. 01:11.390 --> 01:15.330 But the only difference is likes is our 100. 01:15.370 --> 01:15.930 OK. 01:16.100 --> 01:18.550 So that's the only difference between the two. 01:18.560 --> 01:26.230 Now the update method updates the values in the existing document and you can use it by doing D-B collection 01:26.230 --> 01:28.200 in that update. 01:28.280 --> 01:31.720 And then the selection criteria and the updated data. 01:31.720 --> 01:32.110 OK. 01:32.120 --> 01:35.780 So we're going to talk about that and show you some examples. 01:35.780 --> 01:36.040 OK. 01:36.050 --> 01:40.870 So consider them my collection collection which has the following data. 01:40.880 --> 01:44.280 So we have two objects here and then we have one title. 01:44.300 --> 01:49.430 Mongo D-B overview with an ID here and another one with an ID and a title. 01:49.440 --> 01:51.010 OK No.6 overview. 01:51.120 --> 01:51.690 OK. 01:51.800 --> 01:58.940 So basically following example will set the new title new Mongo D-B tutorial of the documents whose 01:58.940 --> 02:00.260 title is Maunganui Baeza. 02:00.260 --> 02:05.160 We're going to replace this title lung would be overview with new Mongo NDB tutorial. 02:05.200 --> 02:05.800 OK. 02:06.140 --> 02:12.080 So we're going to do a DVD on Michael update update and then I'm going to specify the criteria that 02:12.080 --> 02:15.860 I want to that I want to change and or that I want to search for. 02:15.860 --> 02:19.700 In this case I want to search for all the documents that have a title. 02:19.790 --> 02:23.410 Mangu NDB overview and then a comma. 02:23.480 --> 02:26.580 And then what I want to says if you're a member here there's two parts right. 02:26.580 --> 02:31.910 There is a selection criteria so my selection criteria here is that I want the title to have a mango 02:31.910 --> 02:39.060 D-B overview and then in the updated data over here the new data that I want and when I set dollar said 02:39.160 --> 02:45.500 so very important that I'm not to set the title to mean new Mongo IDB tutorial in the dark and then 02:45.500 --> 02:47.590 close the curly brackets. 02:47.600 --> 02:52.690 Now if I show all the documents I'm going to do a DBD on my column data find. 02:52.700 --> 02:57.810 So I'm going to show a scene that an ID is now this same idea over here. 02:58.010 --> 03:01.100 So if you see here this is the same as this ID over here. 03:02.550 --> 03:07.280 But then the title change from Mangu honeybee or wherever you are to new Mago D-B overview. 03:07.440 --> 03:07.970 OK. 03:08.220 --> 03:15.320 And also this one remain the same right because it wasn't inside this selection criteria. 03:15.660 --> 03:19.470 Now by default Mungo will update only a single document. 03:19.470 --> 03:24.170 OK so just make sure you understand the only update a single dog can. 03:24.270 --> 03:30.090 So if you want to update multiple documents you need to set up parameter Multi to true okay. 03:30.150 --> 03:36.710 And the way you do it is and this is a very useful tip is OK how your selection criteria over here. 03:36.750 --> 03:38.640 This is your selection criteria. 03:38.880 --> 03:40.200 And then a comma right. 03:40.290 --> 03:43.960 I hid it from you so there's a comma and then you have a set. 03:44.160 --> 03:49.090 But then before the set if you notice you're used when open the curly brackets right so you have said 03:49.110 --> 03:52.240 over here and then in the end. 03:52.250 --> 03:56.870 After that after you specify you're set right there is a comma another comma. 03:57.000 --> 04:00.040 And then you have another curly brackets with multi Ignaz true. 04:00.120 --> 04:00.600 OK. 04:00.720 --> 04:07.350 So multi as true means that what you're doing essentially is you're saying any document which satis 04:07.410 --> 04:10.080 which has this title mongered me over. 04:10.090 --> 04:17.100 You change all of its titles to new monk would you be DOYLE So not just a single document but all the 04:17.100 --> 04:21.030 documents in in the Mongo D-B. 04:21.030 --> 04:23.100 Now what if we want to delete the dog. 04:23.220 --> 04:27.310 So we thought about updating documents and inserting documents. 04:27.330 --> 04:34.110 What about deleting documents well mongerer need be removed so damali TV has a remove function or method 04:34.110 --> 04:37.110 that is used to remove a document from the collection. 04:37.110 --> 04:39.720 Now remove method access to parameters. 04:39.840 --> 04:45.250 One is the deletion criteria and the second is just one flag. 04:45.420 --> 04:46.230 So what are those. 04:46.260 --> 04:49.680 So the deletion criteria basically says which. 04:49.680 --> 04:57.480 What type of criteria or what kind of conditions must a document have such that it's deleted. 04:57.480 --> 04:57.880 Right. 04:57.960 --> 05:06.150 So for example if I have if I if I inserted the the the the deletion criteria as likes and then 100 05:06.360 --> 05:10.690 then I'm going to delete the documents which have 100 likes. 05:10.710 --> 05:15.040 So they have key as likes and 100 as a value. 05:15.060 --> 05:17.510 Now the just one is an optional parameter. 05:17.520 --> 05:20.350 And if it's true that removes only one document. 05:20.550 --> 05:24.740 But if it's false then it removes all the documents which have 100 likes. 05:24.780 --> 05:33.370 So if just one is true that any post or any document which has 100 likes is deleted from the collection. 05:33.540 --> 05:37.230 But if it's only just one that one of them has only delete. 05:37.500 --> 05:45.720 Now the basic syntax for move is to do D-B collection name don't remove and then deletion criteria. 05:45.720 --> 05:50.670 And if you want to insert the just one that's also optional. 05:50.700 --> 05:52.280 So let's take an example. 05:52.530 --> 05:57.290 So let's say you have a collection with the following data. 05:57.450 --> 06:06.000 You have an ID and an object id and then you also have a title and a and the type corresponding title 06:06.360 --> 06:14.840 and then so Mongo D-B overview and then you have another ID object with ID and a title as Nosenko overview. 06:15.330 --> 06:21.840 Now the following example will remove all the documents from that whose title is Mungo D-B overview. 06:22.840 --> 06:24.250 So you do DBD. 06:24.340 --> 06:26.210 My collections are removed. 06:26.290 --> 06:28.610 Title Mangione overview. 06:28.750 --> 06:33.910 So it searches for all the documents which have a title as Mangione beats this one over here. 06:33.910 --> 06:39.970 Mago Nimi overview and it deletes it so this object here is going to be deleted. 06:39.970 --> 06:46.960 Now if I after I remove them I do a find just to search for all of all the documents I would find only 06:46.960 --> 06:51.680 one document which is the second one because the first one is deleted. 06:51.730 --> 06:53.330 So hopefully this makes sense. 06:55.800 --> 06:57.910 OK so now we're going to talk about projection. 06:57.920 --> 06:59.130 What is projection. 06:59.300 --> 07:05.000 Well a mongo to be a projection means selecting only the necessary data rather than selecting the whole 07:05.000 --> 07:06.730 data of the document. 07:06.800 --> 07:11.820 A document has five fields and you need to only show three that select only three fields from that. 07:11.960 --> 07:12.770 So what does that mean. 07:12.770 --> 07:15.090 So let's suppose you're doing a fine for you. 07:15.130 --> 07:16.250 OK. 07:16.340 --> 07:23.320 For some criteria right now suppose your document is very very big so you suppose your documents you 07:23.340 --> 07:23.960 do right. 07:23.960 --> 07:29.450 This is huge right now and it has a ton of fields ready and its size is big. 07:29.870 --> 07:36.380 Now suppose you only want to have the fields in this huge document and you don't need the rest. 07:36.620 --> 07:41.670 So what projection does is you tell it hey after you find it don't return to me. 07:41.690 --> 07:43.420 Everything in this document right. 07:43.420 --> 07:45.510 Don't return the whole document. 07:45.590 --> 07:51.110 Just return the field that I'm interested about for example the first field in this I could feel that 07:51.110 --> 07:51.480 way. 07:51.480 --> 07:58.130 Mongo doesn't have to copy the entire collection into you know enjoying array to give you but instead 07:58.130 --> 08:03.710 just takes one or two fields that you really need and returns them to you. 08:03.800 --> 08:10.260 Now the Navy's fine method is explained before so it accepts a second optional parameter. 08:10.430 --> 08:13.490 And that is a list of fields that you want to retrieve. 08:13.490 --> 08:19.430 So in Lango AB When you execute fine method it will display all the fields off a document write or display 08:19.430 --> 08:23.900 the whole block and write unified as we saw previously here. 08:23.900 --> 08:30.890 So if I fly quickly show you in this example this displays the entire document but it what if I only 08:30.890 --> 08:35.740 need to see the title and the description what if I don't want the ID tags or likes. 08:35.930 --> 08:37.470 So how do I do that. 08:38.120 --> 08:45.200 So to limit this you need to set a list of fields with value 1 or 0 and this is used to show the fields 08:45.310 --> 08:47.110 while 0 is used to hide the field. 08:47.110 --> 08:54.230 So one shows that tells Mongo and I want that field and zero shows that you don't want that field. 08:54.260 --> 08:55.670 So let's take an example. 08:58.360 --> 09:02.280 So the basic syntax a find method with projection is as follows. 09:02.390 --> 09:04.760 So you knew D-B the collection name. 09:04.760 --> 09:08.020 So my collection for example and then not fine. 09:08.210 --> 09:13.880 And then this is the selection criteria that we always select and then come up and then you give it 09:13.880 --> 09:16.390 another document with key 1. 09:16.520 --> 09:20.090 So you say I want that key give it give it back to me. 09:20.090 --> 09:23.240 So consider the collection my column that has the following data. 09:23.240 --> 09:31.350 So we have again the same collection that has to do documents one with ID title and another with ID 09:31.370 --> 09:33.530 and title and each of them are different. 09:33.540 --> 09:33.980 Right. 09:34.220 --> 09:37.550 Because they have different ideas and they have different titles. 09:37.610 --> 09:41.090 Now the following example would display the title of the document. 09:41.180 --> 09:42.920 While querying the document. 09:42.920 --> 09:49.730 So let's say we don't care about the idea we just want to return the title so I can divvied up my column 09:49.730 --> 09:54.110 that find and then this empty document means I'm looking for all the documents right. 09:54.110 --> 10:00.920 There's no selection criteria so any document passes this right so that empty one means just bring everything 10:00.980 --> 10:07.820 in the collection and then but I only want the title so I'll set the title as one and the ID is yours. 10:07.820 --> 10:14.710 I don't want the ID don't return to me the ID just returned the title as the result of this would be 10:14.710 --> 10:14.950 this. 10:15.050 --> 10:22.730 Over here this is their result will be two documents was the title as Mongo D-B overview and title is 10:22.730 --> 10:23.330 no secret. 10:23.330 --> 10:25.440 So if you notice here there is no ID. 10:25.730 --> 10:30.920 So in other words non-good you just returned to me the fields that I was interested in title and not 10:30.920 --> 10:34.020 ID. 10:34.030 --> 10:36.670 Now there's also a case of limiting records. 10:36.660 --> 10:40.170 Let's say you have a record with 100000 customers. 10:40.200 --> 10:41.840 Right so you don't want long Goody-Goody. 10:41.840 --> 10:49.720 Let's say you do find and then your criteria is in general and you just want to a few examples of records 10:49.790 --> 10:50.360 you don't want. 10:50.360 --> 10:56.810 For example all the 100000 or all like 20000 You just want like 100 or something just to look at the 10:56.810 --> 10:57.410 data. 10:57.590 --> 11:01.650 So to limit the records in longer D-B you need to use limit method. 11:01.760 --> 11:06.980 So the method accepts one number type argument which is the number of documents that you want to be 11:06.980 --> 11:10.310 displayed so the maximum number that you see that you want to see. 11:10.450 --> 11:15.040 So D-B duck collection they find and then to limit number. 11:15.050 --> 11:20.700 So that means that even if this returns you know 300000 records right. 11:20.720 --> 11:22.780 This area over here abridgments three others. 11:22.820 --> 11:26.210 Alan if this is just five then you only see five. 11:26.300 --> 11:34.720 So this prevents it from having you know a gigantic returning gigantic list of documents right. 11:34.910 --> 11:36.220 So let's take an example. 11:36.230 --> 11:39.980 So consider the fall the collection my collection that has the following data. 11:39.980 --> 11:44.250 So again we have one and two we have these two objects the same ones. 11:44.540 --> 11:49.630 And so the following example will display only one document while querying the document. 11:49.790 --> 11:56.840 So Ill do D-B that my collection does fine and then empty criteria so all the documents and I want to 11:56.840 --> 11:59.710 see the title and not the ID. 12:00.050 --> 12:02.360 And I also limit that to one. 12:02.390 --> 12:05.860 So I don't want all the documents I just want to limit that to one. 12:06.050 --> 12:12.320 So it returns to me only one documents even though there's two documents that satisfy this criteria 12:12.770 --> 12:17.730 so I'm limiting the number of returns to only one documents instead of two. 12:17.750 --> 12:23.810 So if you don't specify the number argument in limit method then it will display all the documents from 12:23.810 --> 12:24.630 that collection. 12:24.740 --> 12:29.450 So if you just do a limit and a do like this then it's pointless. 12:29.450 --> 12:35.420 This is like if you not call it it will just display all of the documents from the collection that satisfy 12:35.720 --> 12:37.200 the selection criteria. 12:39.220 --> 12:44.140 Now another thing that you might want to do is to sort some documents so to say in documents in language 12:44.500 --> 12:46.630 you need to use the search function. 12:46.630 --> 12:52.510 So the sort of method this method accepts a document containing a list of fields along with their sorting 12:52.510 --> 12:56.390 order to specify sorting order one or negative one or use. 12:56.410 --> 13:02.480 So one is for ascending order and negative one is for descending order and this is the basic syntax 13:02.560 --> 13:06.970 you do D-B collection that find and then you show it. 13:06.990 --> 13:15.400 So it does sort and then you sort that based on this key over here and then the one means sorted in 13:15.400 --> 13:18.980 ascending order based on this key over here. 13:18.990 --> 13:22.590 So an example might be D-B DOD. 13:22.710 --> 13:25.920 My collection does find. 13:25.950 --> 13:26.490 Right. 13:26.770 --> 13:33.860 And then what sort and then you'd open curly parentheses and this this is find. 13:33.880 --> 13:34.450 Right. 13:35.310 --> 13:38.200 And then this is curly brackets here. 13:38.370 --> 13:43.160 And then you would say likes and then one. 13:43.190 --> 13:48.190 So that means to sort them in ascending order based on the number of likes. 13:48.190 --> 13:50.230 So hopefully that makes sense. 13:51.050 --> 13:54.400 So yeah that's it for Mongo D-B we're going to stop here. 13:54.420 --> 13:58.650 And that will be the last lesson in explaining how Mongo DBI works. 13:58.650 --> 14:02.980 The next set of lessons is basically going to be heading straight into it. 14:02.990 --> 14:09.110 And you know programming something with it just to get used to the syntax and not just cover a you know 14:09.130 --> 14:15.270 theory of the stuff to see how this is really used and how we can use it in building our API. 14:15.600 --> 14:18.470 So yeah we'll stop here and I'll see you in the next video. 14:18.480 --> 14:20.640 So until the next video app decoding.