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Hi and welcome back.
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Till now we have been retrieving data from a single table, so although we had three tables, sales, customer
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and product at a time in a query, we got data from only one of these tables.
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But there is a lot of information that we can get if we could somehow combine the information in these
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tables.
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For example, the sales table has information about each sale transaction.
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And the product table has information about the product.
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We can combine these two tables.
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To find out which category of product is having, how much sales.
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And I'm sure that you can imagine how this kind of information will be helpful in making business decisions.
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So this is achieved by joining that is combining information from multiple tables.
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So joining the data will be covered in the first part of the module.
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The next part is on subqueries. Subqueries are used to do multiple levels of analysis in a single
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query.
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So basically in a single query, as we have already seen, that we can perform certain data operations
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and we can get first level of analysis done.
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Using subquery, you can use the output of this first query that is the result from the first level
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analysis as an input and you can perform next level of operations using this output as your input.
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So you will understand how exactly this is done when we cover this in detail in the second part of this,
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module.
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Then we talk about views and indexes.
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Views are virtual tables built on top of the original database, and these are used for saving space
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and to give limited access of our data to someone else.
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Indexes are used to improve the retrieval speed from our database.
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So views and indexes will be covered in the last part of the module.
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These are some of the advanced concepts of SWL which we are going to cover in this module, but do
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not worry, just follow the lectures and keep practicing side by side.
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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
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the next video.
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