MySQL 查看與修改數據庫字符集編碼：從 latin1 遷移到 utf8mb4

查看當前編碼

USE db_name;
SHOW VARIABLES LIKE 'character_set_database';
+------------------------+--------+
| Variable_name          | Value  |
+------------------------+--------+
| character_set_database | latin1 |
+------------------------+--------+

修改數據庫默認字符集

ALTER DATABASE db_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;

驗證：再次執行 SHOW VARIABLES LIKE 'character_set_database'; 應顯示 utf8mb4。

關鍵說明

• ALTER DATABASE 僅修改**新建表**的默認字符集，**現有表不受影響**
• 需逐表轉換：ALTER TABLE tbl CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
• utf8mb4 支持 4 字節字符（Emoji、生僻字），utf8 僅支持 3 字節，**強烈建議全鏈路使用 utf8mb4**

全鏈路字符集配置清單

# my.ini / my.cnf
[client]
default-character-set = utf8mb4

[mysql]
default-character-set = utf8mb4

[mysqld]
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
init_connect = 'SET NAMES utf8mb4'

應用層連接字符串

• JDBC：jdbc:mysql://host:3306/db?characterEncoding=utf8mb4&useSSL=false
• Python：charset='utf8mb4'
• PHP PDO：charset=utf8mb4