LibreOffice-Suite-Base/C4/Database-Design-Purpose-OrganizeTables/English-timed
From Script | Spoken-Tutorial
Visual Cue | Narration |
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00:00 | Welcome to the Spoken tutorial on LibreOffice Base. |
00:04 | In this tutorial,
we will learn the following topics on database design: |
00:09 | Determining the purpose of our database |
00:12 | Finding and organizing the information required |
00:15 | Dividing the information into tables. |
00:19 | What is Database Design? |
00:21 | Database design is the process of producing a detailed data model of a database. |
00:28 | With a good design, a database can |
00:32 | Provide up-to-date, accurate and complete information |
00:37 | Which means we can ensure integrity of our information at various levels |
00:43 | Meet our needs of data processing and reporting |
00:48 | And easily accommodate change. |
00:51 | The process of database design consists of the following steps |
00:57 | Determine the purpose of our database |
01:00 | Find and organize the information required |
01:04 | Divide the information into tables |
01:07 | Turn information items into columns |
01:11 | Specify primary keys |
01:14 | Set up the table relationships |
01:17 | Refine our design |
01:20 | Apply the normalization rules |
01:23 | And finally, test, run the database, and maintain. |
01:28 | Okay, let us go to the first step which is |
01:32 | Determine the purpose of our database. |
01:35 | Let us consider a simple Library Application. |
01:38 | A library usually has books. |
01:41 | And these books are issued to its registered members. |
01:45 | So we need a Library application to maintain a list of books, and members |
01:51 | And track the issuing of this books to its members. |
01:56 | Our first step is to find and organize the required information. |
02:01 | Here is where we gather all of the types of information we want to record in the database. |
02:09 | Now that we know the purpose of the Library application, let us identify the items here. |
02:17 | There are books. |
02:19 | A Book has a title, an author, a publisher, and a price. |
02:24 | And we can also store the author’s information such as, date of birth and country he or she belongs to. |
02:33 | We can also store the publisher’s name, address and phone. |
02:38 | Also, there are the Library members who have names, phone numbers and addresses. |
02:45 | Now when a book is issued to a member, there is a |
02:49 | book issue date, return date, actual return date and the checked in status. |
02:56 | These individual items are also called attributes. |
03:01 | Each of these attributes represents a potential column in a table. |
03:08 | At this point, we can formulate questions such as: |
03:12 | How do we add information about a set of fresh books supplied to the Library by a publisher? |
03:20 | How do we maintain a list of its members? |
03:25 | What if a member leaves or a member wants to change his/her address? |
03:32 | How do we update the information, when a book is returned by a member? |
03:38 | What kind of reports would we want to produce? |
03:42 | Which books are most read among the readers? |
03:46 | And how do we generate a list of books which are over due to be returned by members who have borrowed them? |
03:55 | Now that we have some details, let us see how we can divide the information into tables. |
04:02 | We will divide our information items or attributes into major entities or subjects. |
04:11 | Each subject then becomes a table. |
04:14 | So the preliminary list of tables looks like the image shown on the screen. |
04:21 | The major subjects or entities shown here are the books and the members. |
04:26 | Therefore, it makes sense to start out with two tables, one for books and one for members. |
04:33 | Let us now look at the Books table in detail. |
04:37 | It has the 10 attributes or columns which we defined earlier: |
04:43 | Title, Author, Publisher, PublisherAddress, PublisherCity, PublisherPhone, PublishYear, Price, AuthorBirthDate and AuthorCountry. |
04:58 | Now let us see how data is displayed in this table. |
05:03 | Notice that, each row or record contains information about the book, its author and its publisher. |
05:13 | Now, there are two flaws in this design. |
05:17 | There can be many books from the same author or the publisher. |
05:23 | So we notice that the author’s details and the publisher’s details have been repeated many times, |
05:31 | which wastes computer disk space. |
05:34 | And a second problem with this design is: |
05:38 | It runs the risk of introducing anomalies in the database. |
05:44 | Now what is an anomaly? |
05:47 | It is simply an error or inconsistency in the database. |
05:53 | There are three types of anomalies: |
05:57 | The first is called an insertion anomaly, |
06:01 | which can occur when a new record is inserted, |
06:06 | Or when certain attributes cannot be inserted into the database without the presence of other attributes. |
06:14 | For example, we will suppose there is a new Publisher called Penguin. |
06:21 | Now our design will not let us insert details about Penguin publishers, until our library can get a hold of at least one book by them. |
06:34 | The second is called the deletion anomaly, |
06:39 | which occurs during the deletion of a record. |
06:43 | Here, the deletion of a row or record in the database deletes more information than we wished to delete. |
06:51 | For example, we see that the Orient Publishers have only one book titled ‘Paradise Lost’, in our library. |
07:01 | Now if we delete this entire record, then we lose all information on Orient Publishers. |
07:10 | And we lose information about the author John Milton as well. |
07:16 | And finally let us see what Update Anomaly is. |
07:21 | It occurs during the updating of a record. |
07:26 | For example, let us suppose that Cambridge Publishers have a new address. |
07:32 | Now, updating the Address column for this Publisher requires us to make a change in more than one place. |
07:40 | In our case, two places. |
07:43 | And if Cambridge supplied a thousand books, then it means, we need to change the address in those thousand records. |
07:54 | And we might accidentally change the address in one place but forget to change it in the other places. |
08:02 | So this can lead to information not being accurate and thereby data integrity is lost. |
08:11 | How do we solve these problems? |
08:14 | We should redesign so that we record each fact just once. |
08:20 | If the same information is repeated in more than one place, then we should place that information in a separate table. |
08:29 | Let us see how. |
08:31 | Now we have split the Books table into Books, Authors and Publisher. |
08:38 | Notice that the columns in each table store facts about that entity or subject only. |
08:47 | This way, we can record the publisher information only once inside the Publisher table. |
08:55 | Similarly, having a separate Authors table allows recording the author information only once. |
09:04 | And we will see how we can link these tables back to the Books table in the next tutorial. |
09:12 | This brings us to the end of this tutorial on the First part of Database Design in LibreOffice. |
09:19 | To summarize, we learned the following topics on database design: |
09:25 | Determining the purpose of our database |
09:28 | Finding and organizing the information required |
09:32 | Dividing the information into tables |
09:36 | Spoken Tutorial Project is a part of the Talk to a Teacher project, supported by the National Mission on Education through ICT, MHRD, Government of India. |
09:48 | This project is co-ordinated by http://spoken-tutorial.org. |
09:54 | More information on the same is available at the following link. |
09:58 | This script has been contributed by Priya Suresh, DesiCrew Solutions.
And this is Soundharya, DesiCrew Solutions, signing off.
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