Original subtitles

0 Hi and welcome back. 1

Till now we have been retrieving data from a single table, so although we had three tables, sales, customer 2

and product at a time in a query, we got data from only one of these tables. 3

But there is a lot of information that we can get if we could somehow combine the information in these 4

tables. 5

For example, the sales table has information about each sale transaction. 6

And the product table has information about the product. 7

We can combine these two tables. 8

To find out which category of product is having, how much sales. 9

And I'm sure that you can imagine how this kind of information will be helpful in making business decisions. 10

So this is achieved by joining that is combining information from multiple tables. 11

So joining the data will be covered in the first part of the module. 12

The next part is on subqueries. Subqueries are used to do multiple levels of analysis in a single 13

query. 14

So basically in a single query, as we have already seen, that we can perform certain data operations 15

and we can get first level of analysis done. 16

Using subquery, you can use the output of this first query that is the result from the first level 17

analysis as an input and you can perform next level of operations using this output as your input. 18

So you will understand how exactly this is done when we cover this in detail in the second part of this, 19

module. 20

Then we talk about views and indexes. 21

Views are virtual tables built on top of the original database, and these are used for saving space 22

and to give limited access of our data to someone else. 23

Indexes are used to improve the retrieval speed from our database. 24

So views and indexes will be covered in the last part of the module. 25

These are some of the advanced concepts of SWL which we are going to cover in this module, but do 26

not worry, just follow the lectures and keep practicing side by side. 27

I am sure that you will not face any difficulty in this part too. So let's do it and I'll see you in 28

the next video.