DELIMITER $$  

CREATE PROCEDURE `databasename`.`update_char_set`()  

BEGIN  
 DECLARE done INT DEFAULT 0;  
 DECLARE t_sql VARCHAR(256);  
 DECLARE tableName VARCHAR(128);  
 DECLARE lists CURSOR FOR SELECT table_name FROM `information_schema`.`TABLES` WHERE table_schema = 'databasename';  
 DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1;  
 OPEN lists;  
 FETCH lists INTO tableName;  
 REPEAT  
    SET @t_sql = CONCAT('ALTER TABLE ', tableName, ' CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci');  
    PREPARE stmt FROM @t_sql;  
    EXECUTE stmt;  
    DEALLOCATE PREPARE stmt;  
 FETCH lists INTO tableName;  
 UNTIL done END REPEAT;  
 CLOSE lists;  
END$$  

DELIMITER ;  

CALL databasename.update_char_set();

如果你不能让你的表转换，或者你的表总是设置为一些非utf8字符集，但你想要utf8，你最好的办法可能是擦掉它，重新开始，并显式地指定:

create database database_name character set utf8;

mysqldump -uusername -ppassword -c -e --default-character-set=utf8 --single-transaction --skip-set-charset --add-drop-database -B dbname > dump.sql
cp dump.sql dump-fixed.sql
vim dump-fixed.sql


:%s/DEFAULT CHARACTER SET latin1/DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci/
:%s/DEFAULT CHARSET=latin1/DEFAULT CHARSET=utf8/
:wq

mysql -uusername -ppassword < dump-fixed.sql

你可以创建sql来更新所有的表:

SELECT CONCAT("ALTER TABLE ",TABLE_SCHEMA,".",TABLE_NAME," CHARACTER SET utf8 COLLATE utf8_general_ci;   ",
    "ALTER TABLE ",TABLE_SCHEMA,".",TABLE_NAME," CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  ") 
    AS alter_sql
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = "your_database_name";

捕获输出并运行它。

阿诺德•丹尼尔斯(Arnold Daniels)的回答更为优雅。

DELIMITER $$  

CREATE PROCEDURE `databasename`.`update_char_set`()  

BEGIN  
 DECLARE done INT DEFAULT 0;  
 DECLARE t_sql VARCHAR(256);  
 DECLARE tableName VARCHAR(128);  
 DECLARE lists CURSOR FOR SELECT table_name FROM `information_schema`.`TABLES` WHERE table_schema = 'databasename';  
 DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1;  
 OPEN lists;  
 FETCH lists INTO tableName;  
 REPEAT  
    SET @t_sql = CONCAT('ALTER TABLE ', tableName, ' CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci');  
    PREPARE stmt FROM @t_sql;  
    EXECUTE stmt;  
    DEALLOCATE PREPARE stmt;  
 FETCH lists INTO tableName;  
 UNTIL done END REPEAT;  
 CLOSE lists;  
END$$  

DELIMITER ;  

CALL databasename.update_char_set();

utf8到utf8mb4:

1.显示所有数据库默认字符集:

SELECT SCHEMA_NAME 'YOUR_DATABASE_NAME', 
default_character_set_name 'charset', 
DEFAULT_COLLATION_NAME 'collation' 
FROM information_schema.SCHEMATA;

2.显示所有表的状态(字符集)，关注列的“collation”:

use YOUR_DATABASE_NAME;    
SHOW TABLE STATUS ;

3.生成转换sql: 转换数据库和所有表utf8mb4,utf8mb4_unicode_ci

USE information_schema;
SELECT CONCAT("ALTER DATABASE `",table_schema,"` CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;") AS _sql
FROM `TABLES` WHERE table_schema LIKE "YOUR_DATABASE_NAME" AND TABLE_TYPE='BASE TABLE' GROUP BY table_schema UNION
SELECT CONCAT("ALTER TABLE `",table_schema,"`.`",table_name,"` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;") AS _sql  
FROM `TABLES` WHERE table_schema LIKE "YOUR_DATABASE_NAME" AND TABLE_TYPE='BASE TABLE' GROUP BY table_schema, TABLE_NAME 
/*include all columns, commonly don't need this.*/
/*
UNION
SELECT CONCAT("ALTER TABLE `",`COLUMNS`.table_schema,"`.`",`COLUMNS`.table_name, "` CHANGE `",column_name,"` `",column_name,"` ",data_type,"(",character_maximum_length,") CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci",IF(is_nullable="YES"," NULL"," NOT NULL"),";") AS _sql 
FROM `COLUMNS` INNER JOIN `TABLES` ON `TABLES`.table_name = `COLUMNS`.table_name WHERE `COLUMNS`.table_schema like "YOUR_DATABASE_NAME" and data_type in ('varchar','char') AND TABLE_TYPE='BASE TABLE' UNION
SELECT CONCAT("ALTER TABLE `",`COLUMNS`.table_schema,"`.`",`COLUMNS`.table_name, "` CHANGE `",column_name,"` `",column_name,"` ",data_type," CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci",IF(is_nullable="YES"," NULL"," NOT NULL"),";") AS _sql 
FROM `COLUMNS` INNER JOIN `TABLES` ON `TABLES`.table_name = `COLUMNS`.table_name WHERE `COLUMNS`.table_schema like "YOUR_DATABASE_NAME" and data_type in ('text','tinytext','mediumtext','longtext') AND TABLE_TYPE='BASE TABLE';
*/

4.运行生成的SQL语句。

5.刷新数据库。

6.检查:

SHOW TABLE STATUS ;