The difference between where and having in sql

The WHERE clause is used to filter the rows of the query results (for individual rows), while the HAVING clause is used to filter the groups produced by the GROUP BY clause (for the aggregated values in the group).

The difference between the WHERE clause and the HAVING clause in SQL

The WHERE clause and the HAVING clause are both Conditions used in SQL to filter data, but they apply to different data levels:

WHERE clause

• Applies to a single row in the data set
• Used to filter individual rows of query results
• Apply conditions to specific column values in rows
• Use before the GROUP BY clause

HAVING clause

• Applies to groups generated by the GROUP BY clause
• Used to filter groups created based on the GROUP BY clause
• Apply conditions to aggregate values in a group (e.g., SUM, COUNT, etc.)
• Use after the GROUP BY clause

Example

WHERE clause:

SELECT * FROM customers WHERE age > 25;

This query will return all customer rows with an age greater than 25.

HAVING clause:

SELECT region, COUNT(*) AS total_orders FROM orders GROUP BY region HAVING total_orders > 100;

This query will return zone groups where the total number of orders exceeds 100.

The above is the detailed content of The difference between where and having in sql. For more information, please follow other related articles on the PHP Chinese website!