group by having usage example

The GroupBy Having clause is used to filter grouped data. It first groups the data and then filters the results according to the specified conditions. Common usages include:

1. Find the sum or average of a particular group.
2. Find groups that meet certain criteria.
3. Perform aggregation calculations on grouped data, such as summing, average or counting.

GroupBy Having usage examples

The GroupBy Having clause is a syntax used in SQL to filter grouped data. It is used with the GroupBy clause, first grouping the data, and then filtering the grouped results based on specified conditions.

grammar:

 <code>SELECT列名1,列名2, ... FROM表名GROUP BY分组列HAVING筛选条件</code>

Examples of usage:

Suppose we have a table sales containing product sales data, which contains product_id , product_name , quantity and total_sales columns. Now, we want to find out the number of each product with a total sales of more than 10,000.

Query:

 <code>SELECT product_id, product_name, COUNT(DISTINCT quantity) AS product_count FROM sales GROUP BY product_id HAVING SUM(total_sales) > 10000</code>

How does this query work?

1. GroupBy clause : It groups data according to product_id , grouping records with the same product ID together.
2. Having clause : It checks each group and filters it according to condition SUM(total_sales) > 10000 . Only groups that meet this condition will be returned.
3. COUNT(DISTINCT quantity) : It calculates the number of unique values ​​in quantity column in each group, which represents the number of times each product is sold.

result:

This query will return the number of each product that meets the following criteria:

• Total sales exceed $10,000

The output may be as follows:

product_id	product_name	product_count
1	Product A	10
2	Product B	5

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