Question

我有一个带有While的存储过程，在这个While中，我需要从动态SQL语句创建一个视图。对于第一次迭代，我的视图包含良好的结果，但followinf迭代始终具有主要结果，而不是与新的预准备语句相对应的行...

如果我将WHILE替换为使用@a的不同值的创建视图的2倍，结果将达到预期。关于While的准备好的语句似乎是一个问题...

DROP PROCEDURE IF EXISTS bug;
DELIMITER | 
CREATE PROCEDURE bug()
BEGIN
   DECLARE a INT(1);
   DECLARE s VARCHAR(100) DEFAULT '';

   SET @a = 1;

   WHILE @a <= 2 DO

      SET @s = concat('CREATE OR REPLACE VIEW bugview as SELECT ',@a,';');

      select concat('@s=',@s);

      PREPARE stmt FROM @s;
      EXECUTE stmt;
      DEALLOCATE PREPARE stmt;

      select @a;
      select * from bugview;

      set @a = @a + 1;
   END WHILE;
END|
DELIMITER ;

错误的结果（在最后一张表上，期望值应为2而不是1）：

+------------------------------------------------+
| concat('@s=',@s)                               |
+------------------------------------------------+
| @s=CREATE OR REPLACE VIEW bugview as SELECT 1; |
+------------------------------------------------+
1 row in set (0.00 sec)

+------+
| @a   |
+------+
|    1 |
+------+
1 row in set (0.01 sec)

+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.01 sec)

+------------------------------------------------+
| concat('@s=',@s)                               |
+------------------------------------------------+
| @s=CREATE OR REPLACE VIEW bugview as SELECT 2; |
+------------------------------------------------+
1 row in set (0.01 sec)

+------+
| @a   |
+------+
|    2 |
+------+
1 row in set (0.02 sec)

+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.02 sec)

在While中使用准备好的语句创建视图似乎无法正常工作

0 个答案: