In what sequence is this SQL query executed (query plan)?.

The sequence of executing an SQL query (logical plan) is usually as follows:

1. FROM — selecting tables and performing joins.
2. WHERE — filtering rows based on a condition.
3. GROUP BY — grouping data.
4. HAVING — filtering grouped data.
5. SELECT — selecting necessary columns and calculating expressions.
6. DISTINCT — removing duplicates.
7. ORDER BY — sorting the result.
8. LIMIT / OFFSET — limiting the number of returned rows.

This is a logical order, which may differ from the physical plan; the optimizer can change the order of operations to improve performance.

Example:

SELECT department, COUNT(*)
FROM employees
WHERE salary > 50000
GROUP BY department
HAVING COUNT(*) > 5
ORDER BY department;

Here, employees with a salary > 50000 are selected first, then they are grouped by department, groups with more than 5 employees are filtered, and finally, the result is sorted by department.