 So, there are students in this module I will define what a database is, so what is a database? The students the list of students in a class is that a database? I don't think it's a database or the students taking certain course is that a database or the record about myself is that a database? Assuming it's digital, it's not a database, so in the context of this course we define a database what constitutes a database, now remember if it's a list of students who are enrolled in a class for a certain semester there is not much change in the students if there is a change one can just write with a pen or pencil a student drops out crosses that list or students adds that course write the name of the student, so that's not really a database but if we are looking at the cars that are parked in a parking lot if you maintain a list of the cars coming in and the cars going and you start cutting the type list of the cars parked and the new cars coming in and start writing it it will create a lot of problem and it's if it's a valet parking then there's a long list of people turning the line so for that you need a database I think you get the picture now let's go into more details, so a database is a body of digital data is a body of single record is not a database right now a database can be defined can be looked at in the context of the data itself or the application software or the custom built application so or it can be a combination also, so when we look at a database it is owned and created by the users owned and created by the users and it is a large collection because it's a small collection why put in a lot of resource no point in it right, so a body of digital data is a database similarly the software to store a data is also called as a database but as a database management system and who creates that DBMS that is created by developers working in a established commercial organization like Oracle like Microsoft and so on so that's another definition of a database then it can be a combination of above okay it can be a combination of above and it can also include custom reports applications developed for custom relationship management CRM applications developed for human resource custom interfaces custom reports and so on so a database is a combination can be a combination of all of them I think you now understand so what are the attributes of a database handles large structured data not unstructured data structured data means that we know that this is the name and this is the ID and the ID of a student is numeric okay and this is the sequence in which we have these things and it will go into the corresponding locations in the database single record is not a database database changes quickly as I gave the example earlier the students in a class don't change a lot during the semester there's a drop and add time after there are hardly any changes so in a true database things are changing very quickly for example I'm using my mobile phone to make calls right now backend database for that company telecommunication company changes are making are done or are made hundreds of changes are happening in seconds in part of a second so that is a database can select and display data in different ways the student list I gave you the example so I have this student ID or the row number first name last name that is static list in a database I would like to see maybe the student names based on their first name the list displayed based on the first name the list displayed based on the last name or the address or a certain combination also so these attributes are in a database that's what we call a database in the context of this course and of course stored versus retrieved right so you can store and you can so you store the data in a certain order the retrieval order can be very different from the way it was stored so this this is the attribute of a database it's case ad hoc more attributes of a database have tools to manipulate data store data retrieve data display data update data so a dbms provides the tools the database contains data about the data itself like the name of the attributes the number of the tables the size of the tables and so on and so on so that is there's the metadata in a database data validation is done is the data entered is unique based upon a certain key called the primary key or is the data of a certain person entered who is a member of a certain club or a company or my customer data is also shared across time and space time and space over here means that the contents of the database change over time over here also for example i am making telephone calls so my balance is changing of course i am not very frequently drawing and depositing money from a bank account but for my mobile phone it is changing and data can be related to one other through links which is called as the certain foreign key relationship right or not and then of course finally if the data is stored okay in a consistent format for example at the at the id i am storing the student id not the customer id not the id of an object if i am storing the customer id at the student id then this is not efficient storage it is not proper storage it will not give me good performance so it has to be similar structured and a database is described by record by field and by key record is a row okay a record is a row or it is also called a tuple and of course then i have this attribute the time at which a call was made the time at which the call was completed okay the package that was used the number called from the number called to those are the attributes those are the fields okay and every row has a field every row has a field and then is a key the key is a a certain id which is unique based upon which every record is identified for example if i'm making calls from my phone my phone is not the that call id is the key which can be generated automatically by the database itself and then there are different methods for making the database to run efficiently to run quickly to give a good response time but that is not mandatory it may come surprising to you of course this process of making the databases run efficiently is called as normalization but you can get performance without normalization also and of course there are applications where normalization is not done but further discussion is beyond the scope of this course so that's all i have for this module thank you