The difference between where and having in sql

WHERE and HAVING clauses are both used to filter data in SQL, but their scopes are different: the WHERE clause filters single rows, and the HAVING clause filters grouped result sets. The WHERE clause is applied before grouping and affects the result rows of the aggregate function; the HAVING clause is applied after grouping and affects grouped rows rather than individual rows. The WHERE clause can filter any column, while the HAVING clause can only filter the results of aggregate functions.

The difference between WHERE and HAVING clauses

In SQL queries, WHERE and HAVING clauses are used for filtering rows of data, but they have different scopes and uses.

WHERE clause

• Applies to a single row of the table.
• Used to filter out rows that meet specified conditions.
• Apply before data grouping.
• Affects the result rows of aggregate functions.

HAVING clause

• Apply to the grouped result set.
• Used to filter out groups that meet specified conditions.
• Apply after data grouping.
• Affects grouped rows rather than individual rows.

Comparison table

Features	WHERE clause	HAVING sub Sentence
Scope	Single line	Group
Application timing	Before grouping	After grouping
Influence	Aggregation function result row	Group row

Example

The following query uses the WHERE clause to filter out orders with sales exceeding 1,000:

SELECT * FROM orders WHERE sales_amount > 1000;

The following query uses HAVING The clause filters out all customers whose average sales exceed 1000:

SELECT customer_id, AVG(sales_amount) AS avg_sales
FROM orders
GROUP BY customer_id
HAVING avg_sales > 1000;

Notes

• The WHERE clause can filter any column, while the HAVING clause only Ability to filter the results of aggregate functions.
• The HAVING clause is usually used together with the GROUP BY clause, while the WHERE clause can be used independently.

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