如何更改MySQL表的默认字符集？

Question

有一个MySQL table,其定义取自SQLYog Enterprise:

Table              Create Table                                             
-----------------  ---------------------------------------------------------
etape_prospection  CREATE TABLE `etape_prospection` (                       
                     `etape_prosp_id` int(10) NOT NULL AUTO_INCREMENT,      
                     `type_prosp_id` int(10) NOT NULL DEFAULT '0',          
                     `prosp_id` int(10) NOT NULL DEFAULT '0',               
                     `etape_prosp_date` datetime DEFAULT NULL,              
                     `etape_prosp_comment` text,                            
                     PRIMARY KEY (`etape_prosp_id`),                        
                     KEY `concerne_fk` (`prosp_id`),                        
                     KEY `de_type_fk` (`type_prosp_id`)                     
                   ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=latin1  

我想default charset将此表的更改latin1为utf8.怎么做 ？

Answer 1

如果要将表default character set和所有字符列更改为新字符集,请使用如下语句:

ALTER TABLE tbl_name CONVERT TO CHARACTER SET charset_name;

所以查询将是:

ALTER TABLE etape_prospection CONVERT TO CHARACTER SET utf8;

Answer 2

更改表的默认字符集:

ALTER TABLE etape_prospection
  CHARACTER SET utf8,
  COLLATE utf8_general_ci;

要更改字符串列charset,请更改此查询:

ALTER TABLE etape_prospection
  CHANGE COLUMN etape_prosp_comment etape_prosp_comment TEXT CHARACTER SET utf8 COLLATE utf8_general_ci;

Answer 3

在ALTER TABLEMySQL命令应该做的伎俩.以下命令将更改表的默认字符集,并将其所有列的字符集更改为UTF8.

ALTER TABLE etape_prospection CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;

此命令将表中的所有类似文本的列转换为新的字符集.字符集每个字符使用不同数量的数据,因此MySQL将转换某些列的类型以确保有足够的空间来容纳与旧列类型相同数量的字符.

我建议您在修改任何实时数据之前阅读ALTER TABLE MySQL文档.

Answer 4

如果有人正在寻找一个完整的解决方案来更改所有数据库表的默认字符集并转换数据，这可能是一个：

DELIMITER $$

CREATE PROCEDURE `exec_query`(IN sql_text VARCHAR(255))
BEGIN
  SET @tquery = `sql_text`;
  PREPARE `stmt` FROM @tquery;
  EXECUTE `stmt`;
  DEALLOCATE PREPARE `stmt`;
END$$

CREATE PROCEDURE `change_character_set`(IN `charset` VARCHAR(64), IN `collation` VARCHAR(64))
BEGIN
DECLARE `done` BOOLEAN DEFAULT FALSE;
DECLARE `tab_name` VARCHAR(64);
DECLARE `charset_cursor` CURSOR FOR 
    SELECT `table_name` FROM `information_schema`.`tables`
    WHERE `table_schema` = DATABASE() AND `table_type` = 'BASE TABLE';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET `done` = TRUE;

SET foreign_key_checks = 0;
OPEN `charset_cursor`;
`change_loop`: LOOP
FETCH `charset_cursor` INTO `tab_name`;
IF `done` THEN
    LEAVE `change_loop`;
END IF;
CALL `exec_query`(CONCAT(
  'ALTER TABLE `',
  tab_name,
  '` CONVERT TO CHARACTER SET ',
  QUOTE(charset),
  ' COLLATE ',
  QUOTE(collation),
  ';'
));
CALL `exec_query`(CONCAT('REPAIR TABLE `', tab_name, '`;'));
CALL `exec_query`(CONCAT('OPTIMIZE TABLE `', tab_name, '`;'));
END LOOP `change_loop`;
CLOSE `charset_cursor`;
SET foreign_key_checks = 1;
END$$

DELIMITER ;

您可以将此代码放入文件中，例如chg_char_set.sql并通过从 MySQL 终端调用它来执行它：

SOURCE ~/path-to-the-file/chg_char_set.sql

然后使用所需的输入参数调用定义的过程，例如

CALL change_character_set('utf8mb4', 'utf8mb4_bin');

测试结果后，您可以删除这些存储过程：

DROP PROCEDURE `change_character_set`;
DROP PROCEDURE `exec_query`;