What is the difference between having and where in SQL?

2 years ago
Olivia Parker
2 minutes

In SQL, HAVING and WHERE are two key words used for filtering data. Their differences are as follows:

  1. The WHERE clause is used to filter data before a query, and it is applied after the FROM clause and before the GROUP BY clause. It filters row data based on column conditions to restrict the returned data rows. Various operators (such as equals, greater than, less than) and logical operators (such as AND, OR) can be used in the WHERE clause.
  2. The HAVING clause is used to filter grouped data after the GROUP BY clause. It filters based on the results of grouping, allowing the use of aggregate functions (such as SUM, AVG, COUNT, etc.) and logical operators. The HAVING clause filters the results after grouping.

One way to understand the difference between these two key terms is to consider the following query examples:

SELECT column1, SUM(column2)
FROM table
WHERE condition
GROUP BY column1
HAVING condition

In this query, the WHERE clause is used to filter row data, while the HAVING clause is used to filter results after grouping. Use the WHERE clause if the condition only involves column data; use the HAVING clause if the condition involves aggregate functions or grouped results.

In summary, the WHERE clause filters row data, while the HAVING clause filters results after grouping.

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