 So, students in this module, I will discuss briefly of course normalization. If you recall that in the previous module, number 103, we ended at normalization and the purpose of normalization was to efficient make efficient database access to enhance the performance. And of course, we will be looking at the normal forms which are there when we perform this normalization. So, let's look at that. So, we have of course, there are five normal forms and then there are additional ones also. I'll cover the basic four ones in this module. So, why we do normalization? Let's explain it to you using certain examples and then things would be clear to you. Okay, first normal form. Now, look at this simple table layout over here. So, why we have this table layout? Because say for example, people come for appointment, it's a doctor's database, and people come for appointment and this appointment is based upon the time and the location and the title. Of course, that doctor has different clinics at different locations. Okay, and the title is that for which job that person is coming for which kind of a treatment. Now, what is evident from table one table one is very this is very basic kind of a table to store is that there are repeating groups over here. We have this, this is getting repeated. This is getting repeated over here. So, this is a lot of wastage of space. So, this is one reason why we need to have the first normal form. Then is if we if we are looking to perform a search. Now, the thing is that if we are doing a search, say for example on name is equal to X, okay. Now, there can be multiple people who might be having this kind this X over here, okay, there can be multiple people. So, which X are we talking about? The big question mark over here. What happens that everybody comes up with their own solutions. So, there are diversity of solutions and those diversity is not very formal and the end user can make some suggestions or some people say put multiple values in a column which is against their relational model and so on. So, the most the best solution is or the right solution is two tables. Okay. So, we have this table over here and we have this table over here. And as you can see over here is that there is no limit. We don't have to assign any space over here. Okay, we don't say that for 10 appointments, okay. Or say for 50 appointments or like five appointments. So, the number of appointments can can vary. So, these are just those rows are added in this appointment database. And over here, we have this name of that person which was X over here, right. So, there is no ambiguity why there is no ambiguity because now we have the sequence number over here. And that sequence number is the primary key. That is the unique base upon which we can combine these tables. So, that is why we need the first normal phone. Now, what happens is that there are many instances. There are many examples. There are many cases that we cannot place the data in very nicely in the type of the solution I showed you in the last slide, okay. So, not all databases can be organized as in the table two, okay. Now, what would be the example of repeating group in the case of table number three, okay. Now, is this a repeating group or this is a repeating group, okay. This is a repeating group. So, this is not very simple. Now, remember one thing that is when we have this repeating group, right. And it is consuming space. Now, when we split the repeating groups, we split the repeating groups. Of course, that results in saving of the space, but there is a slight processing time also because we have to refer two tables. We just call it a join also. So, we have to take into consideration. The space time trade-off vis-a-vis the web-based application. So, you have to take into this thing the account. Therefore, we are performing this normalization, okay. Now, second normal form. Now, when we have now anybody who is kind of a new to this domain would say, I can store all the data in one table. Why use two tables? The purpose of two tables is synchronization of this redundant data. Because if you have a single table and you have repeating, then if there's a change, you have to make the change everywhere. So, if you don't do this second normal form, what will happen that UK have, you may have two different accounts on the single credit card, which is wrong. So, we are not only trying to save space, but only also ensuring that the data is entered only once. The benefit, another benefit is that if the item have been shipped and there is a change in the address, you don't have to make that change everywhere, only at one place. So, that is the benefit of this second normal form. Now, the third normal form and the fourth normal form, let me briefly talk about the third normal form, is that if I have the table in which I have the zip code and the name of the town also, then there's a dependency between the zip code and the town. Because in many cases, say for example, the customer may only provide you the zip code or only provide you the town name, right? So, it would be kind of incomplete. So, if there is dependency, we remove that dependency. And in what happens is that the zip code table is separate, the name of the town corresponding to that zip code it isn't a separate table. I think you get that point. So, what would be the benefit that it would be incomplete versus simple design? Now, for the zip code case, there are not many, many towns, they're not like in hundreds and thousands, they are less than that, significantly less than that. So, we can have this simple design, right? But for other scenarios, say for example, I have a customer database, I have a million customers, and then they have these appointments, for example, for this insurance company, then this kind of thing is not going to work. And finally, the fourth normal form, is that say for example, there is a meeting at a certain time and at a certain place between two people. Now, the question is, is that a joint meeting or it's a conflict? So, that conflict is considered over here and that's why we are saying that two types of relations are not allowed. So, that is the fourth normal form. So, that's all I have for you in this module. Thank you very much.