我已經將我的問題簡化為這個簡單的SP。列名在最后被緩存在SELECT *中。我不知道為什么或如何阻止它。我嘗試添加SQL_NO_CACHE，但這沒有什么區別。

DROP TABLE IF EXISTS foo;

CREATE TABLE foo(

col1 int,

col2 int);

INSERT INTO foo VALUES(1,2),(3,4),(5,6);

DROP PROCEDURE IF EXISTS mysp;

DELIMITER ;;

CREATE DEFINER=root@localhost PROCEDURE mysp(c INT)

BEGIN

DROP TABLE IF EXISTS mydata;

SET @mycol='col1';

IF c > 0 THEN SET @mycol:='col2';

END IF;

SET @s=CONCAT('CREATE TEMPORARY TABLE mydata AS SELECT ', @mycol, ' FROM foo');

PREPARE stmt FROM @s;

EXECUTE stmt;

DEALLOCATE PREPARE stmt;

-- The following select call fails on 2nd and subsequent executions of the SP

SELECT SQL_NO_CACHE * FROM mydata;

SELECT "Please see new temp table mydata" as Result;

END ;;

DELIMITER ;版

mysql> SELECT VERSION();

+------------+

| VERSION() |

+------------+

| 5.5.15-log |

+------------+

1 row in set (0.00 sec)首次運行如預期般運作良好

mysql> CALL mysp(0);

+------+

| col1 |

+------+

| 1 |

| 3 |

| 5 |

+------+

3 rows in set (0.17 sec)

+----------------------------------+

| Result |

+----------------------------------+

| Please see new temp table mydata |

+----------------------------------+

1 row in set (0.17 sec)

Query OK, 0 rows affected (0.17 sec)現在，如果我嘗試使用另一列再次運行它

mysql> CALL mysp(1);

ERROR 1054 (42S22): Unknown column 'qlgqp1.mydata.col1' in 'field list'

mysql> SELECT @mycol;

+--------+

| @mycol |

+--------+

| col2 |

+--------+

1 row in set (0.00 sec)如果我再次重新創建存儲過程它的作品

mysql> CALL mysp(1);

+------+

| col2 |

+------+

| 2 |

| 4 |

| 6 |

+------+

3 rows in set (0.18 sec)

+----------------------------------+

| Result |

+----------------------------------+

| Please see new temp table mydata |

+----------------------------------+

1 row in set (0.18 sec)

Query OK, 0 rows affected (0.18 sec)但是，如果我嘗試切換回第一列 - 即使我先嘗試刪除臨時表 - 它仍然不起作用

mysql> CALL mysp(0);

ERROR 1054 (42S22): Unknown column 'qlgqp1.mydata.col2' in 'field list'

mysql> DROP TABLE mydata;

Query OK, 0 rows affected (0.03 sec)

mysql> CALL mysp(0);

ERROR 1054 (42S22): Unknown column 'qlgqp1.mydata.col2' in 'field list'

mysql>*附加信息請求eggyal。另外我在另一個mysql版本上嘗試了這個結果。 *

mysql> CALL mysp(1);

+------+

| col2 |

+------+

| 2 |

| 4 |

| 6 |

+------+

3 rows in set (0.20 sec)

+----------------------------------+

| Result |

+----------------------------------+

| Please see new temp table mydata |

+----------------------------------+

1 row in set (0.20 sec)

Query OK, 0 rows affected (0.20 sec)

mysql> describe mydata;

+-------+---------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-------+---------+------+-----+---------+-------+

| col2 | int(11) | YES | | NULL | |

+-------+---------+------+-----+---------+-------+

1 row in set (0.00 sec)

mysql> CALL mysp(0);

ERROR 1054 (42S22): Unknown column 'test.mydata.col2' in 'field list'

mysql> describe mydata;

+-------+---------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-------+---------+------+-----+---------+-------+

| col1 | int(11) | YES | | NULL | |

+-------+---------+------+-----+---------+-------+

1 row in set (0.00 sec)有趣的修補程序開發 - 將最后幾行更改為準備好的語句 - 但使用與以前完全相同的查詢。

-- The following select call fails on 2nd and subsequent executions of the SP

PREPARE stmt FROM 'SELECT SQL_NO_CACHE * FROM mydata';

EXECUTE stmt;

DEALLOCATE PREPARE stmt;

SELECT "Please see new temp table mydata" as Result;

總結

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