1 00:00:02,110 --> 00:00:05,689 Now that's it for this course section. 2 00:00:05,689 --> 00:00:06,910 In this course section, 3 00:00:06,910 --> 00:00:10,450 you got a thorough introduction into SQL 4 00:00:10,450 --> 00:00:13,470 and the kind of databases that use that language. 5 00:00:13,470 --> 00:00:15,690 Most importantly, MySQL, 6 00:00:15,690 --> 00:00:18,223 which we installed and started working with. 7 00:00:19,210 --> 00:00:20,530 Though, I want to mention again, 8 00:00:20,530 --> 00:00:23,450 that what you learned about the SQL Syntax in this 9 00:00:23,450 --> 00:00:27,390 section here, will apply to all the SQL databases 10 00:00:27,390 --> 00:00:28,770 you might be using. 11 00:00:28,770 --> 00:00:33,200 It's a very popular and common database system, 12 00:00:33,200 --> 00:00:36,160 and therefore definitely a system or a language, 13 00:00:36,160 --> 00:00:39,210 you have to know when being a Web Developer. 14 00:00:39,210 --> 00:00:42,730 You'll learn that when you work with a relational database 15 00:00:42,730 --> 00:00:46,550 management system, as we did it here in this course section, 16 00:00:46,550 --> 00:00:50,590 that it's all about working with different tables. 17 00:00:50,590 --> 00:00:54,060 Storing your data in a normalized form, 18 00:00:54,060 --> 00:00:57,820 which means in a simplified form, where you have no complex 19 00:00:57,820 --> 00:01:01,290 data in a single table across multiple tables, 20 00:01:01,290 --> 00:01:06,290 linked together through IDs or other unique identifiers, 21 00:01:06,570 --> 00:01:08,973 as we did it in this course section. 22 00:01:10,560 --> 00:01:13,490 And you then learn how you can run commands to create 23 00:01:13,490 --> 00:01:17,100 tables, to insert data into tables, 24 00:01:17,100 --> 00:01:21,120 to update or delete data, and of course, to query data. 25 00:01:21,120 --> 00:01:23,140 To query data just like that, 26 00:01:23,140 --> 00:01:26,890 or with constraints or counting the data that's 27 00:01:26,890 --> 00:01:28,313 in a database table. 28 00:01:29,420 --> 00:01:33,230 And then since we do work with multiple tables, of course, 29 00:01:33,230 --> 00:01:35,630 you also learned about the very important 30 00:01:35,630 --> 00:01:38,840 inner join statement, which allows you to 31 00:01:38,840 --> 00:01:42,880 merge data together in your result sets 32 00:01:42,880 --> 00:01:46,530 with which you then might be working in your applications. 33 00:01:46,530 --> 00:01:49,197 So that you can answer questions like, 34 00:01:49,197 --> 00:01:53,210 what's the name of the restaurant that has a rating of five? 35 00:01:53,210 --> 00:01:54,313 For example. 36 00:01:56,090 --> 00:01:59,300 Now coming back to these relationships. 37 00:01:59,300 --> 00:02:00,960 In this core section, 38 00:02:00,960 --> 00:02:04,180 we saw the one to many relationship and action, 39 00:02:04,180 --> 00:02:08,410 which means that one record in table A can be related to 40 00:02:08,410 --> 00:02:11,163 multiple records in table B. 41 00:02:11,163 --> 00:02:12,390 For example, 42 00:02:12,390 --> 00:02:15,260 that a single restaurant can have multiple reviews, 43 00:02:15,260 --> 00:02:18,253 but every review belongs to only one restaurant. 44 00:02:19,540 --> 00:02:22,910 There also are other kinds of relationships. 45 00:02:22,910 --> 00:02:26,300 For example, one-to-one relationships. 46 00:02:26,300 --> 00:02:28,490 There, you would have one record 47 00:02:28,490 --> 00:02:30,370 in table A that's related to 48 00:02:30,370 --> 00:02:33,080 exactly one other record in table B, 49 00:02:33,080 --> 00:02:36,000 and not more than one record. 50 00:02:36,000 --> 00:02:39,400 An example could be a team that has one team leader, 51 00:02:39,400 --> 00:02:43,900 and that team leader leads exactly one team and team leaders 52 00:02:43,900 --> 00:02:47,163 and team data is stored in different tables. 53 00:02:48,820 --> 00:02:50,010 And last but not least, 54 00:02:50,010 --> 00:02:53,310 you could also have many to many relationships, 55 00:02:53,310 --> 00:02:55,880 which is a bit more advanced and therefore was not 56 00:02:55,880 --> 00:02:58,810 covered here, but which you will always encounter, 57 00:02:58,810 --> 00:03:03,100 if you dive deeper into web development and take dedicated 58 00:03:03,100 --> 00:03:07,120 sequel courses or deep dive courses in general. 59 00:03:07,120 --> 00:03:11,070 The idea behind many to many relationships is that a record 60 00:03:11,070 --> 00:03:14,860 in table A can be related to multiple records in table B 61 00:03:14,860 --> 00:03:16,709 and vice versa. 62 00:03:16,709 --> 00:03:19,660 To handle this with a SQL database, 63 00:03:19,660 --> 00:03:21,850 you would have an intermediate table 64 00:03:21,850 --> 00:03:24,020 that stores the connections. 65 00:03:24,020 --> 00:03:25,390 And an example would be, 66 00:03:25,390 --> 00:03:27,410 a restaurant that has many customers 67 00:03:27,410 --> 00:03:31,120 and every customer might visit many restaurants. 68 00:03:31,120 --> 00:03:32,660 This is just a side note here. 69 00:03:32,660 --> 00:03:34,350 It's not too important. 70 00:03:34,350 --> 00:03:37,070 And we will come back to these relationships later 71 00:03:37,070 --> 00:03:39,730 in the course, once we do dive in deeper. 72 00:03:39,730 --> 00:03:43,940 And once we do build our online shop, for example. 73 00:03:43,940 --> 00:03:46,400 I just wanted to mention them here already, 74 00:03:46,400 --> 00:03:50,670 because of course a main feature off SQL databases of 75 00:03:50,670 --> 00:03:53,960 relational database management systems, 76 00:03:53,960 --> 00:03:56,090 as the name already implies, I guess, 77 00:03:56,090 --> 00:03:59,440 is that you do work with relationships and that you do 78 00:03:59,440 --> 00:04:01,863 relate data from different tables. 79 00:04:02,840 --> 00:04:05,890 And therefore now, with that in the next chord section, 80 00:04:05,890 --> 00:04:08,930 we're going to see how we can now actually use what we 81 00:04:08,930 --> 00:04:10,680 learned in this section, 82 00:04:10,680 --> 00:04:15,680 inside of a real application, inside of node JS code. 83 00:04:15,830 --> 00:04:18,910 So that we don't have to write all the queries here in the, 84 00:04:18,910 --> 00:04:22,380 MySQL workbench, which is nice for playing around, 85 00:04:22,380 --> 00:04:26,310 but which isn't a real application and that we instead see 86 00:04:26,310 --> 00:04:30,640 how we can actually do work with the database from inside 87 00:04:30,640 --> 00:04:32,293 our node JS code.