How to use GROUP BY and HAVING clauses to group and filter data?

The GROUP BY clause in SQL is used to group records that have the same values in specified columns into summary rows. It is often used with aggregate functions like COUNT(), SUM(), AVG(), etc., to perform calculations on each group.

The HAVING clause is used in conjunction with GROUP BY to filter the groups based on a condition. Unlike the WHERE clause, which filters individual records before grouping, HAVING filters groups after aggregation.

Example:

Assume you have a table named Sales with the following data:

Product	Amount
A	10
B	20
A	30
B	40
C	50

Using GROUP BY:

To find the total amount sold for each product, you would use:

SELECT Product, SUM(Amount) as TotalAmount
FROM Sales
GROUP BY Product;

This would result in:

Product	TotalAmount
A	40
B	60
C	50

Using HAVING:

If you want to find only those products where the total amount sold is greater than 45, you would use the HAVING clause:

SELECT Product, SUM(Amount) as TotalAmount
FROM Sales
GROUP BY Product
HAVING SUM(Amount) > 45;

This would result in:

Product	TotalAmount
B	60

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