错误解决mysql - Event Scheduler: No data - zero rows fetched, selected, or processed

标签：

  DECLARE CONTINUE HANDLER FOR NOT FOUND
    BEGIN
　　　 SET done=1
      SELECT 1 INTO @handler_invoked FROM (SELECT 1) AS t;
    END;

Before MySQL 5.6.3, if a statement that generates a warning or error causes a condition handler to be invoked, the handler may not clear the diagnostic area. This might lead to the appearance that the handler was not invoked. The following discussion demonstrates the issue and provides a workaround.

Suppose that a table t1 is empty. The following procedure selects from it, raising a No Data condition:

CREATE PROCEDURE p1()
BEGIN
  DECLARE a INT;
  DECLARE CONTINUE HANDLER FOR NOT FOUND
    BEGIN
      SET @handler_invoked = 1;
    END;
  SELECT c1 INTO a FROM t1;
END;

As can be seen from the following sequence of statements, the condition is not cleared by handler invocation (otherwise, the SHOW WARNINGS output would be empty). But as can be seen by the value of @handler_invoked, the handler was indeed invoked (otherwise its value would be 0).

mysql> SET @handler_invoked = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> CALL p1();
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> SHOW WARNINGS;
+---------+------+-----------------------------------------------------+
| Level   | Code | Message                                             |
+---------+------+-----------------------------------------------------+
| Warning | 1329 | No data - zero rows fetched, selected, or processed |
+---------+------+-----------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT @handler_invoked;
+------------------+
| @handler_invoked |
+------------------+
|                1 |
+------------------+
1 row in set (0.00 sec)

To work around this issue, use a condition handler containing a statement that clears warnings:

CREATE PROCEDURE p1()
BEGIN
  DECLARE a INT;
  DECLARE CONTINUE HANDLER FOR NOT FOUND
    BEGIN
      SELECT 1 INTO @handler_invoked FROM (SELECT 1) AS t;
    END;
  SELECT c1 INTO a FROM t1;
END;

This works for CONTINUE and EXIT handlers.

This issue is resolved as of MySQL 5.6.3 and no workaround is needed.

错误解决mysql - Event Scheduler: No data - zero rows fetched, selected, or processed

标签：

原文地址：http://www.cnblogs.com/gamir/p/4307772.html