 Students, in this module, I will be talking about certain things that matter and they matter a lot in the context of a web-based database applications. In the context of bringing the data on the web, remember that the systems have been around the database systems, these systems predate the web, their issues because those systems were not meant to bring the data on the web or to make web-enabled database applications, which I have also touched upon in the prior module. So I will talk about it more in this module. I will also discuss in this module the DDL, Data Definition Language, or the commands of the SQL, which are insert, update, and delete and of course I will talk more about them. This is the hole which I will be covering in this module and this is the coverage of this module. So I would again suggest you because I am covering the key points, discovering and discussing with you the key points, now it is your duty and as a student to read the notes to understand and comprehend and of course if you have queries, you can raise the queries. Understand? So let's now go ahead. Why this matters? It matters because queries may already exist, this is fine, it is very good that I have to bring a database on the web and the queries exist, very wonderful, this is very nice, but the thing is may not be able to create the queries, the queries don't exist, which is more of a reality, the queries don't exist and either unable to create the queries as a web developer or queries don't exist at all, those queries are not provided. So if there are no queries, it's a big question mark and how to bring the data on the web? Okay, when the database people cannot provide you the queries and you cannot convert those queries into a web environment, you have to work on it. Then there are the standard queries, then it is fine. Standard queries is that you are displaying multiple things or one thing or so on. So those standard queries can be implemented, that is the one way out. And then there are the specialized queries focused on making a selection based upon certain selection criteria and why this matters? Because tables and field names are needed. The thing is that field names may be misleading. So for example, there are two tables and they have the same field name, but the meanings are different. They can be many examples. Okay. And so this is misleading. So you cannot just look at the field names and you can conclude that the field names are same. So their meaning is also same. That may not be true. And there is no uniformity. If you are a new person, believe it and you should experience it. There is no uniformity in the things. And users are wanting to refine the database, which you have designed. So these are some of the realities of bringing your database to the web. Why these things matter? Common keys may not exist or match. Okay. Remember that in the previous module, as we spoke about connecting the tables to avoid the duplication on those common keys, which is the primary key. Now the primary key may not exist. Okay. Or they don't match. That the data which needs to be displayed on your website has not been collected, has not been organized, has not been accumulated for this purpose. And the accounting people or the accounting system or the payroll system or the inventory system, those, those systems don't talk to each other. This is the domain of data warehousing. Okay. Which is the core CS614. So web-based database, it is a collaborative effort. So this is a fence. So you have these database people at one end and you have yourself, which is the web people at one end, across the fence. So you have to cross this fence and those that fence can be crossed used using the queries and communicate and understand the problems and the needs of the database people. And the, and of course you, you have to translate those, the, what you get into the web queries and ensure one thing that make all parties happy, make all parties happy. Who are the parties? The parties are the database people who provide you the queries. The party is your customer also. The customer for which you are developing that application. The party is those people who come on the website, which is a very public area to view the results or to get the results they are interested in. I think you understand now. So the DDL statements insert, delete and update. Nothing not to explain, not to give a lot of details over here. But the thing is that it is validated means, it is validated means that you have to ensure that what is being sent to the server to do the operation. Okay, that has to be checked. And of course this data is collected by the user form. For example, if the, if somebody is inserting their data. Okay, we are, remember I am talking about those old databases. So you, you cannot offer buttons or dropped on menus and all that kind of useful functionality. So it's a box in which the user types in the text which needs to be entered. So it needs to be validated. And the difference between this is that it modifies the existing rows. Okay, now create has a number of flavors also. For example, using the create, you can create the views over here. You can create the indices also. So a view is like a temporary table, which actually does not exist. But it is not known to the user that it is, it doesn't exist. So whenever a query is run on the view that view is generated. Okay, and of course, indices are not created by the user and user. The indices are created by the database administrator which speed up the database access, make it quick. Okay, and unless and unless it is sluggish. Okay, it is not your domain to talk to the somebody who will talk to the database administrator to make the things run faster. That is all I have for this module.