WEBVTT 1 00:00:00.300 --> 00:00:03.060 Let's select everything from our books table again. 2 00:00:03.060 --> 00:00:07.740 We have an ID, which is a unique identifier for the database entry. 3 00:00:07.740 --> 00:00:12.590 This is a common practice and guarantees that every row is not a duplicate of 4 00:00:12.590 --> 00:00:16.910 another, and can be isolated from all other rows if needed. 5 00:00:16.910 --> 00:00:22.820 We have the title, author, genre, and first_published. 6 00:00:22.820 --> 00:00:26.140 Remember, querying a table's contents allows us to present 7 00:00:26.140 --> 00:00:29.030 the results of a database in many different ways. 8 00:00:29.030 --> 00:00:32.070 The results are designed for humans to read. 9 00:00:32.070 --> 00:00:35.270 But sometimes the column names aren't that friendly. 10 00:00:35.270 --> 00:00:38.980 Let's say I was running a query for the library administrator. 11 00:00:38.980 --> 00:00:42.624 They want a report of all the books in the database along with the year that they 12 00:00:42.624 --> 00:00:43.759 were first published. 13 00:00:47.642 --> 00:00:50.870 The column headers are all in lower case. 14 00:00:50.870 --> 00:00:53.140 This may be distracting to the report reader. 15 00:00:53.140 --> 00:00:58.190 We can change the title of any column, by using the keyword AS. 16 00:00:58.190 --> 00:01:02.770 After the AS, you can write what you want to alias the column name to. 17 00:01:02.770 --> 00:01:05.370 Let's use Title with an uppercase T. 18 00:01:06.530 --> 00:01:10.340 When we run the query now, we get the results back with a capital T 19 00:01:10.340 --> 00:01:12.300 in the title column. 20 00:01:12.300 --> 00:01:15.551 How about the first_published column? 21 00:01:15.551 --> 00:01:20.970 We can use the AS keyword again but with the words First Published. 22 00:01:23.570 --> 00:01:26.178 If you try and execute this query, you'll get an error. 23 00:01:26.178 --> 00:01:29.240 Error: near "Published": syntax error. 24 00:01:29.240 --> 00:01:33.210 The key for us here is that it's a syntax error. 25 00:01:33.210 --> 00:01:35.420 Remember the syntax is the grammar or 26 00:01:35.420 --> 00:01:39.140 the rules surrounding the way we write programming code. 27 00:01:39.140 --> 00:01:42.500 The computer doesn't understand the word Published. 28 00:01:42.500 --> 00:01:47.890 It's expecting a FROM or a comma, followed by another column name. 29 00:01:47.890 --> 00:01:51.380 We can't use multiple words like this when writing SQL queries. 30 00:01:52.570 --> 00:01:57.980 So what do we do for something such as our first_published alias, in our reports? 31 00:01:57.980 --> 00:02:00.510 There is a way we can use some punctuation, 32 00:02:00.510 --> 00:02:03.910 which is part of the SQL syntax, to solve this problem. 33 00:02:03.910 --> 00:02:10.407 We can define column names with spaces by wrapping them in quotes like this. 34 00:02:10.407 --> 00:02:13.601 The opening quote is just before the first letter, and 35 00:02:13.601 --> 00:02:16.040 the closing quote after the last letter. 36 00:02:17.740 --> 00:02:19.380 But here's another got ya. 37 00:02:19.380 --> 00:02:22.840 Writing SQL in different databases like Microsoft SQL, or 38 00:02:22.840 --> 00:02:28.610 PostgreSQL my require you to use different punctuation for writing aliases. 39 00:02:28.610 --> 00:02:32.870 Some require single quotes, others even require square brackets. 40 00:02:32.870 --> 00:02:38.360 The SQL we're using in SQL Playground can use double quotes, but just be mindful. 41 00:02:38.360 --> 00:02:43.700 SQL in different settings may have these slight variations in syntax. 42 00:02:43.700 --> 00:02:47.512 Most database documentations have help to guide you around these difficulties. 43 00:02:47.512 --> 00:02:51.360 When we execute this query now, we see Title and 44 00:02:51.360 --> 00:02:55.590 First Published with a space as the column titles. 45 00:02:55.590 --> 00:02:59.973 There is a short hand for this syntax, where you remove the AS keyword. 46 00:03:02.749 --> 00:03:05.672 You can try it too. 47 00:03:05.672 --> 00:03:06.472 See? 48 00:03:06.472 --> 00:03:08.320 It's the same results. 49 00:03:08.320 --> 00:03:11.440 I avoid this syntax because it's not very clear. 50 00:03:11.440 --> 00:03:12.740 I just wanted to bring you up so 51 00:03:12.740 --> 00:03:15.730 you weren't confused if you saw it somewhere else. 52 00:03:15.730 --> 00:03:19.960 To recap, to alias a column name to something of your choosing, 53 00:03:19.960 --> 00:03:25.280 type SELECT <column name> the keyword AS, followed by the new name. 54 00:03:27.020 --> 00:03:32.230 So, if I were to bring back all patron names in a more user-friendly format, 55 00:03:32.230 --> 00:03:34.080 I could do something like this. 56 00:03:34.080 --> 00:03:39.048 With quotes around the first name and last name. 57 00:03:42.860 --> 00:03:46.430 These characters surrounded by quote marks are called strings, 58 00:03:46.430 --> 00:03:48.450 meaning strings of characters, 59 00:03:48.450 --> 00:03:52.310 letters, numbers, special characters and spaces. 60 00:03:52.310 --> 00:03:55.070 One final note about the AS keyword. 61 00:03:55.070 --> 00:03:59.710 When you bring back data with a new label using the AS keyword 62 00:03:59.710 --> 00:04:03.370 it does not change the name of the column in the actual database. 63 00:04:03.370 --> 00:04:07.680 For example, when we aliased our first_published column 64 00:04:07.680 --> 00:04:10.770 as First Published in our report. 65 00:04:10.770 --> 00:04:14.380 The column name is always first_published. 66 00:04:14.380 --> 00:04:18.880 Only in our report do we see the column represented as First Published. 67 00:04:18.880 --> 00:04:22.220 This is why we call it an alias. 68 00:04:22.220 --> 00:04:27.230 As an aside, the AS keyword can be used to alias table names for 69 00:04:27.230 --> 00:04:30.910 more complex queries working with multiple tables. 70 00:04:30.910 --> 00:04:33.060 We'll be covering that in another course.