How to use having in mysql

Use the HAVING clause to filter groups in MySQL grouping queries: limit the scope of the group and filter the group based on the group aggregate value, such as finding customer groups with an average order value greater than $100. Compare group aggregate values, such as finding groups of customers with a total order count greater than 10. Use aggregate functions like SUM(), AVG(), COUNT(), etc. The difference with the WHERE clause is that the WHERE clause filters individual rows, while the HAVING clause filters groups.

Usage of HAVING clause in MySQL

The HAVING clause is used to filter groups in grouped queries . It is similar to the WHERE clause, but is used to filter groups of data rather than individual rows.

Syntax:

<code class="sql">SELECT ...
GROUP BY ...
HAVING condition</code>

Usage:

1. Limit the scope of the group: HAVING clause can be used to filter groups based on group aggregate values. For example, to find a group of customers with an average order value greater than $100:

<code class="sql">SELECT customer_id
FROM orders
GROUP BY customer_id
HAVING AVG(order_value) > 100;</code>

2. Compare group aggregate values: The HAVING clause can also be used to compare group aggregate values. For example, to find customer groups with a total order count of more than 10:

<code class="sql">SELECT customer_id
FROM orders
GROUP BY customer_id
HAVING COUNT(*) > 10;</code>

3. Use aggregate functions: Aggregate functions can be used in the HAVING clause, such as SUM(), AVG( ), COUNT(), etc.
4. Differences from the WHERE clause: The WHERE clause is used to filter individual rows, while the HAVING clause is used to filter groups. This means that the WHERE clause is applied before grouping and the HAVING clause is applied after grouping.

Example:

Get the average price of each product category and only show categories with an average price greater than $100:

<code class="sql">SELECT category_name, AVG(product_price) AS average_price
FROM products
GROUP BY category_name
HAVING average_price > 100;</code>

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