我們如何建立MySQL預存程序來計算階乘？

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mysql> DELIMITER //
mysql> CREATE PROCEDURE get_factorial(IN N INT)
    -> BEGIN
    ->    SET @@GLOBAL.max_sp_recursion_depth = 255;
    ->    SET @@session.max_sp_recursion_depth = 255;
    ->
    ->    CALL factorial_recursive (N, @factorial);
    ->
    ->    SELECT @factorial;
    -> END //
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER //
mysql> CREATE PROCEDURE factorial_recursive(IN N INT,OUT factorial INT)
    -> BEGIN
    ->    IF N = 1 THEN
    ->       SET factorial := 1;
    ->    ELSE
    ->       CALL factorial_recursive (N-1, factorial);
    ->       SET factorial := N * factorial;
    ->    END IF;
    -> END //
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER ;
mysql> Call get_factorial(10);
+--------------+
| @factorial   |
+--------------+
|      3628800 |
+--------------+
1 row in set (0.11 sec)
Query OK, 0 rows affected (0.12 sec)

mysql> Call get_factorial(5);
+-------------+
| @factorial  |
+-------------+
|         120 |
+-------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)

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