MySql - 不支持BLOB/TEXT列

Question

create temporary table if not exists tmp engine=memory 
SELECT id, CONCAT(TRIM(lastName),TRIM(firstName),TRIM(zip)) AS identify
FROM customers 
GROUP BY identify;

在运行该程序时，我收到以下错误信息：

The used table type doesn't support BLOB/TEXT columns

我已经看过这个线程，但它没有帮助我。

这些列的类型如下:

lastName -> VARCHAR(255)
firstName -> VARCHAR(255)
zip -> VARCHAR(10)

如果我从程序中排除zip，那么它就能正常工作，所以我猜测varchar的长度可能存在问题？

有没有人知道不更改zip的varchar长度从10到255的解决方案？

- rockZ

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你不能直接将计算后的值转换回VARCHAR()吗？ - Álvaro González

Answer 1

发生率由常量CONVERT_IF_BIGGER_TO_BLOB的值表示：

/**
  CHAR and VARCHAR fields longer than this number of characters are converted
  to BLOB.
  Non-character fields longer than this number of bytes are converted to BLOB.
  Comparisons should be '>' or '<='.
*/
#define CONVERT_IF_BIGGER_TO_BLOB 512   /* Used for CREATE ... SELECT */

mysql-server/sql/sql_const.h::52

并且

16.3 MEMORY存储引擎

• ...

• 不支持变长数据类型（包括BLOB和TEXT）。

示例：

mysql> DROP TEMPORARY TABLE IF EXISTS `tmp`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TEMPORARY TABLE IF NOT EXISTS `tmp` ENGINE=MEMORY
    -> SELECT SPACE(512) `tmp_col`;
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> DROP TEMPORARY TABLE IF EXISTS `tmp`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TEMPORARY TABLE IF NOT EXISTS `tmp` ENGINE=MEMORY
    -> SELECT SPACE(513) `tmp_col`;
ERROR 1163 (42000): The used table type doesn't support BLOB/TEXT columns

尝试：

mysql> DROP TABLE IF EXISTS `tmp`, `customers`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE IF NOT EXISTS `customers` (
    ->   `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->   `lastName` VARCHAR(255) NOT NULL,
    ->   `firstName` VARCHAR(255) NOT NULL,
    ->   `zip` VARCHAR(10) NOT NULL
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TEMPORARY TABLE IF NOT EXISTS `tmp` (
    ->   `id` BIGINT UNSIGNED NOT NULL PRIMARY KEY,
    ->   `identify` VARCHAR(520) NOT NULL
    -> ) ENGINE=MEMORY;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO `tmp`
    -> SELECT `id`, CONCAT(TRIM(`lastName`),
    ->                     TRIM(`firstName`),
    ->                     TRIM(`zip`)) `identify`
    -> FROM `customers`
    -> GROUP BY `id`, `identify`;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

- wchiquito

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非常感谢您的研究和解决方案！ - rockZ

Answer 2

我的经验是使用ENGINE=MEMORY时字符集也很重要。 varchar(65000) 采用latin1字符集可以工作，但采用UTF8字符集则不行。 ENGINE=MEMORY DEFAULT CHARSET=latin1

- matjung

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非常感谢。 - Moin Uddin