mysql数据库乱码怎么修改

-- 查看数据库字符集
SHOW CREATE DATABASE your_database_name;

-- 修改数据库字符集
ALTER DATABASE your_database_name CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- 查看表字符集
SHOW CREATE TABLE your_table_name;

-- 修改表字符集
ALTER TABLE your_table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- 查看列字符集
SHOW FULL COLUMNS FROM your_table_name;

-- 修改列字符集
ALTER TABLE your_table_name MODIFY your_column_name VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

String url = "jdbc:mysql://localhost:3306/your_database_name?charset=utf8mb4";
Connection conn = DriverManager.getConnection(url, "username", "password");