MySQL8使用with recursive实现递归

MySQL8使用with recursive实现递归

语法

WITH recursive 表名 AS ( 
	初始语句（非递归部分） 
	UNION ALL 
	递归部分语句
)
[ SELECT| INSERT | UPDATE | DELETE]

案例

1.输出1 ~ n

WITH recursive t AS 
(
	SELECT 1 AS n 
	UNION ALL 
	SELECT n + 1 FROM t WHERE n < 10
) 
SELECT * FROM	t;

结果

2.输出n的阶乘

WITH recursive t AS (
	SELECT 1 AS n, 1 AS factorial 
	UNION ALL
	SELECT n + 1,	( n + 1 ) * factorial FROM t WHERE n < 10 
)
SELECT * FROM	t;

结果

3.输出前n项和

WITH recursive t AS ( 
	SELECT 1 AS n, 1 AS sum 
	UNION ALL 
	SELECT n + 1, n + 1 + sum FROM t WHERE n < 10 
) 
SELECT * FROM	t;

结果