 So students in this module, we will cover data modeling. What is data modeling? The data modeling is the process of understanding and comprehending and recording and making sure what we need to do with the data. What we want to do on the data, it's not about how we are going to do it, it's not about the operations. I think you understand what we want to do and what is required to be done on the data, not about the operations itself. This is the data modeling. So we have a conceptual data model, we have the logical data model, we have the physical data model, similarly that we have the schemas also. Now there's a difference between the schema and the model because when we say schema, we are going into very into a lot of details with reference to the model. So I'm going to explain these things in this module. So we have the database schema and we have the database model. So database schema gives the nitty gritty details about the database blueprint offered it, just like the architect provides the map with the nitty gritty details that is in the schema. It contains the formulas, it records the formulas and through and what we are doing constraints defines the relationships which I'll discuss. So I have this entity which was a student, I had that entity which was the course and there is a relationship between them. That is the relationship I'm talking about, define the relationships. Now the data model is of three types which I just mentioned and it provides a conceptual framework and it can be relational. It can be non-relational also when we move to the module about the Cords rules, then I'll explain in a lot of details the 0 to 13 or the 0 to 12 number Cords rules. What is a relational database? So it can be relational. It may not be relational. Now let me explain these three models using simple example. So before I go into explaining these examples, let's look at the process, how we go about. So I have these entities. Entity is something which is of importance in the real world and that entity has an attribute like the student is an entity, student name, age, phone number, address are the attributes and the relationships like course is an entity, so the relationship between course is taken by the students. So with this, I have this conceptual data modeling and using this substantial data modeling, I have to do the logical data model. So what is in the logical data model? I have the process models, okay. How things are going to be done and I have these data requirements. So when I want to do certain thing, what I would need? I need to compute the age of the student, say for example, the GPA of the student, so I need to have the date of birth of the student to compute the age. I need to have the grades to compute the GPA. Once I have this logical data model, then I go to the physical modeling and in the physical modeling, I need to have these representations of the data, how indexing will be performed, which indexing will be done about the security of the data, about the integrity of the data. So I have these things, requirements which are going into the physical data model and then I have this actually application running, which is developed based upon these models. You see that it's a process through which additional details are being added to make it more comprehensible to make it more useful for the developer and nothing is missed. That is the purpose, because the cost of fixing the things missed is tremendous as compared to doing it the first right time. So let's look at this example over here. So the conceptual data model, I have this customer, customer is an entity. I have this product, product is an entity, every customer has a name, okay. I have this customer number or customer ID also, I have this product, product can also have an ID, it is not shown over here, but can have an ID and of course the product has a price, okay. And what is the relationship between a customer and a product? That a product is sold to a customer and a customer purchases a product. So you see the level of detail in this conceptual data model. Then I have this logical data model. So I am assigning the type of data, which is associated with the customer name, which is a string, okay. And then I have this customer number, which is an integer, it is not a real number. Okay. Similarly, I have this product price, which is an integer in this case, and you see that the I have associated the data type with the attributes of the entity and also note that this notation has changed. And then I have this physical data model. Now I am going to more nitty-gritty details that before in the in the in the prior model, it was not, it was just said, okay, it was text. Now I am telling which type of text, type of text, okay. And this customer number is still an integer, but now I am saying that it is a primary key. The primary key is something which uniquely identifies a record, a customer in this case. Okay. Similarly, I have this unique product name over here. So the point over here is based upon this product name. This can be identified. So what does this model does? It model keys, constraints, indexes, triggers, and many other things. You see the level of detail goes increasing as we move ahead in this model. What are the advantages of this modeling? Accurate representation. If we follow this process, we are unlikely to miss the things. And this helps in building the physical database where the data is actually going to be stored. It takes care of the tables. The tables are defined. The primary key is defined. The foreign key is defined. Foreign key is a relationship that if I would like to add a student, assign a student to a course, that student must be registered, student of the university. And this is easy to understand and communicate with the business. And they recognize the correct data sources where the data is available, which is going to be used, to be processed, and to be reflected in this model. And finally, we see that there's no standard data, DML is data manipulation language. There's no standard DML for the databases. And it needs extensive factual knowledge. You need to have people who knows all those things, who knows the issues and the relationships. And they have the factual knowledge also. And they can communicate that knowledge also. So it is a challenge. But that's why we are here. That's why you are taking this course. That's why I'm explaining these things to the people who develop and expertise in taking up these challenges. They are going to be the winners. Thank you for your time.