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Introduction
Reports with revenue in categories
Revenue in time periods for selected categories
Summary

## Instruction

Good! Let's get started. There are two queries which we can use for total revenue as follows:

SELECT SUM(Amount) AS TotalRevenue FROM Orders;

Or:

SELECT SUM(Amount) AS TotalRevenue FROM OrderItems;

Now, let's say we want to show the history-to-date revenue for various categories:

CategoryName TotalRevenue
Seafood 131261.75
Meat/Poultry 163022.37
Condiments 106047.11

Such a report can help us discover which product categories are more profitable. In this case, we can only use the second query (the one with the OrderItems table). Take a look:

SELECT
CategoryName,
SUM(Amount) AS TotalRevenue
FROM OrderItems OI
JOIN Products P
ON OI.ProductId = P.ProductId
JOIN Categories C
ON P.CategoryId = C.CategoryId
GROUP BY CategoryName;


This query is a bit more complicated because we had to join OrderItems with Products and Categories to get the category names used in the report.

## Exercise

Run the template query and see how it generates a row with the history-to-date revenue for each category.