What is the difference between WHERE and HAVING?

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Both filter rows, but at different stages of query execution. WHERE — filters rows before grouping and aggregation. Cannot reference aggregate functions like SUM() or COUNT() . HAVING — filters groups after GROUP BY has been applied. Can reference aggregate results. Order of execution: FROM &rarr; WHERE &rarr; GROUP BY &rarr; HAVING &rarr; SELECT &rarr; ORDER BY . WHERE = before GROUP BY (rows), HAVING = after GROUP BY (groups). WHERE cannot use aggregates. HAVING can. This is the #1 most asked SQL filtering question. Know the execution order: FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT.