What is the difference between WHERE and HAVING in MySQL?

2 years ago
Benjamin Taylor
2 minutes

In MySQL, WHERE and HAVING are keywords used for filtering data, but they have slightly different uses and functionalities.

  1. The WHERE clause is used in a query to specify conditions for filtering row data. It is placed after the FROM clause and before the GROUP BY clause in the SELECT statement. The WHERE clause can use column names, operators, and values to build conditions, then filter out the rows as needed. For example:
SELECT column1, column2
FROM table_name
WHERE condition;
  1. The HAVING clause is used in a query to specify conditions for filtering data after grouping. It follows the GROUP BY clause. The HAVING clause can use aggregate functions, column names, operators, and values to create conditions, then filter out the groups that meet those conditions. The HAVING clause is commonly used together with the GROUP BY clause to filter grouped data. For example:
SELECT column1, COUNT(column2)
FROM table_name
GROUP BY column1
HAVING condition;

Difference:

  1. The WHERE clause filters the data before the query, applying to the original dataset.
  2. The HAVING clause filters the data after the query is executed and is applied to grouped data.
  3. Conditions in the WHERE clause can include column names, operators, and values.
  4. Conditions in the HAVING clause can include aggregate functions, column names, operators, and values.
  5. The WHERE clause can be used in any query, while the HAVING clause can only be used in queries that include a GROUP BY clause.
  6. The WHERE clause filters row data, while the HAVING clause filters grouped data.

In general, the WHERE clause is used to filter row data, while the HAVING clause is used to filter grouped data.

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