在SQL中,FOR循环并不是一个内置的功能
WITH RECURSIVE factorial_cte (n, result) AS (
SELECT 0, 1
UNION ALL
SELECT n + 1, result * (n + 1) FROM factorial_cte WHERE n < 5
)
SELECT result FROM factorial_cte WHERE n = 5;
WITH RECURSIVE numbers_cte (number) AS (
SELECT 1
UNION ALL
SELECT number + 1 FROM numbers_cte WHERE number < 10
)
SELECT number FROM numbers_cte;
WITH RECURSIVE fibonacci_cte (n, value) AS (
SELECT 0, 0
UNION ALL
SELECT 1, 1
UNION ALL
SELECT n + 1, value + LAG(value) OVER (ORDER BY n) FROM fibonacci_cte WHERE n < 10
)
SELECT value FROM fibonacci_cte ORDER BY n;
WITH RECURSIVE org_hierarchy_cte (employee_id, manager_id, employee_name, level) AS (
SELECT employee_id, manager_id, employee_name, 1
FROM employees
WHERE manager_id IS NULL
UNION ALL
SELECT e.employee_id, e.manager_id, e.employee_name, oh.level + 1
FROM employees e
JOIN org_hierarchy_cte oh ON e.manager_id = oh.employee_id
)
SELECT employee_name, level FROM org_hierarchy_cte ORDER BY level, employee_name;
这些示例展示了如何使用递归公共表表达式(CTE)来模拟FOR循环的行为。请注意,这些查询可能需要根据您的数据库系统进行调整。