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 ;

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 ;

在继续之前，请确保您:已完成完全数据库备份!

步骤1:数据库级别更改

标识数据库的排序规则和字符集 选择default_character_set_name, default_collation_name from information_schema。图式年代 WHERE schema_name = 'your_database_name' 和 (DEFAULT_CHARACTER_SET_NAME != 'utf8' 或 DEFAULT_COLLATION_NAME不像'utf8%'); 修复数据库的排序规则 ALTER DATABASE DATABASE utf8 COLLATE utf8_unicode_ci;

步骤2:表级别更改

Identifying Database Tables with the incorrect character set or collation SELECT CONCAT( 'ALTER TABLE ', table_name, ' CHARACTER SET utf8 COLLATE utf8_general_ci; ', 'ALTER TABLE ', table_name, ' CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci; ') FROM information_schema.TABLES AS T, information_schema.`COLLATION_CHARACTER_SET_APPLICABILITY` AS C WHERE C.collation_name = T.table_collation AND T.table_schema = 'your_database_name' AND (C.CHARACTER_SET_NAME != 'utf8' OR C.COLLATION_NAME not like 'utf8%') Adjusting table columns' collation and character set

捕获上层sql输出并运行它。(如后)

ALTER TABLE rma CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
ALTER TABLE rma_history CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma_history CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
ALTER TABLE rma_products CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma_products CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
ALTER TABLE rma_report_period CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma_report_period CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
ALTER TABLE rma_reservation CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma_reservation CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
ALTER TABLE rma_supplier_return CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma_supplier_return CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
ALTER TABLE rma_supplier_return_history CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma_supplier_return_history CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
ALTER TABLE rma_supplier_return_product CHARACTER SET utf8 COLLATE utf8_general_ci;ALTER TABLE rma_supplier_return_product CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci; 

参考网址:https://confluence.atlassian.com/display/CONFKB/How+to+Fix+the+Collation+and+Character+Set+of+a+MySQL+Database

如果数据不在相同的字符集中，您可以考虑http://dev.mysql.com/doc/refman/5.0/en/charset-conversion.html中的这个片段

如果列具有非二进制数据类型(CHAR、VARCHAR、TEXT)，则其 内容应该在列字符集中编码，而不是其他字符集 字符集。如果内容用不同的字符编码 设置后，您可以先将列转换为使用二进制数据类型，然后 然后转换到具有所需字符集的非二进制列。

这里有一个例子:

 ALTER TABLE t1 CHANGE c1 c1 BLOB;
 ALTER TABLE t1 CHANGE c1 c1 VARCHAR(100) CHARACTER SET utf8;

确保选择正确的排序规则，否则可能会得到唯一的键冲突。如。 Éleanore和Eleanore在某些排序中可能被认为是相同的。

旁白:

我曾遇到过这样的情况，电子邮件中的某些字符“坏了”，尽管它们在数据库中以UTF-8格式存储。如果您使用utf8数据发送电子邮件，您可能还需要将电子邮件转换为utf8发送。

在phpailer中，只需更新这一行:public $CharSet = 'utf-8';

受@sdfor注释的启发，这里有一个bash脚本可以完成这项工作

#!/bin/bash

printf "### Converting MySQL character set ###\n\n"

printf "Enter the encoding you want to set: "
read -r CHARSET

# Get the MySQL username
printf "Enter mysql username: "
read -r USERNAME

# Get the MySQL password
printf "Enter mysql password for user %s:" "$USERNAME"
read -rs PASSWORD

DBLIST=( mydatabase1 mydatabase2 )

printf "\n"


for DB in "${DBLIST[@]}"
do
(
    echo 'ALTER DATABASE `'"$DB"'` CHARACTER SET utf8 COLLATE `'"$CHARSET"'`;'
    mysql "$DB" -u"$USERNAME" -p"$PASSWORD" -e "SHOW TABLES" --batch --skip-column-names \
    | xargs -I{} echo 'ALTER TABLE `'{}'` CONVERT TO CHARACTER SET utf8 COLLATE `'"$CHARSET"'`;'
) \
| mysql "$DB" -u"$USERNAME" -p"$PASSWORD"

echo "$DB database done..."
done

echo "### DONE ###"
exit

你也可以使用数据库工具Navicat，这样做更容易。

湿 婆。

右键单击您的数据库，并在下拉菜单中选择数据库属性和更改