LibreOffice-Suite-Base/C4/Database-Design-Purpose-OrganizeTables/English-timed

Time	Narration
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 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 coordinated 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. Thanks for joining.

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sandhya.np14