Having

The SQL HAVING clause is a component of the SQL SELECT statement that allows you to filter the results of an aggregation based on a specific condition. In other words, it enables you to apply conditions to grouped data after the GROUP BY clause has been applied.

The HAVING clause is similar to the WHERE clause, but while the WHERE clause filters data based on individual rows, the HAVING clause filters data based on groups. As a result, the HAVING clause is typically used in conjunction with the GROUP BY clause.

Syntax

The syntax of the HAVING clause is as follows:

SELECT column_name, 
aggregate_function(column_name)
FROM table_name
WHERE condition
GROUP BY column_name
HAVING condition;

In this syntax, the GROUP BY clause groups the data based on the specified column, and the aggregate function is applied to the grouped data. The HAVING clause then filters the results of the aggregation based on the specified condition.

Example

For example, suppose you have a table called “sales” with columns “product”, “salesperson”, and “amount”, and you want to find the total sales for each product where the total sales are greater than $10,000. You can use the following SQL statement:

SELECT product, SUM(amount) as total_sales
FROM sales
GROUP BY product
HAVING SUM(amount) > 10000;

In this example, the SUM function calculates the total sales for each product, and the HAVING clause filters the results to only include products with a total sales greater than $10,000.

In conclusion, the HAVING clause is a powerful tool in SQL that allows you to filter the results of an aggregation based on a specific condition. It is typically used in conjunction with the GROUP BY clause to group data and apply aggregate functions.