How to use having in sql

HAVING clause is used to filter grouped data. The syntax is: SELECT aggregate_functions(column_name) FROM table_name GROUP BY column_name HAVING condition;. It can filter on aggregate functions, grouping columns, constants or operators. For example, the following query filters out groups with at least 3 items in the order and a total amount greater than $100: SELECT COUNT(DISTINCT order_id) AS order_count FROM orders GROUP BY cus

The HAVING clause in SQL

#The role of the HAVING clause:

The HAVING clause is used to filter grouped data . It is similar to the WHERE clause, but is used to filter aggregated results rather than raw data.

The syntax of the HAVING clause:

<code>SELECT aggregate_functions(column_name)
FROM table_name
GROUP BY column_name
HAVING condition;</code>

Conditions:

The conditions in the HAVING clause can include the following:

• Aggregation functions (e.g. SUM, COUNT, AVG)
• Group columns
• Constant
• Operators (e.g. >, <, =)

Usage of HAVING clause:

HAVING clause can be used in a variety of scenarios, for example:

• Filter out groups that meet specific conditions from grouped results
• Find groups with specific aggregate values ​​(such as maximum value, minimum value)
• Calculate percentages or averages based on aggregation results

Example:

Query orders that meet the following conditions:

• The total amount is greater than 100 US dollars
• The order contains at least 3 items

SELECT COUNT(DISTINCT order_id) AS order_count
FROM orders
GROUP BY customer_id
HAVING SUM(total_amount) > 100 AND COUNT(DISTINCT product_id) >= 3;
Note: 

The HAVING clause can only be used after the GROUP BY clause. 
HAVING clause can only filter aggregate results, not original data. 


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