在MySQL中动态选择列

-- 创建表
CREATE TABLE `employees` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(30) NOT NULL,
  `age` int(11) NOT NULL,
  `salary` decimal(10,2) NOT NULL,
  PRIMARY KEY (`id`)
);

-- 插入数据
INSERT INTO `employees` (`name`, `age`, `salary`) VALUES ('John', 30, 50000.00);
INSERT INTO `employees` (`name`, `age`, `salary`) VALUES ('Jane', 25, 60000.00);

-- 创建预处理语句
PREPARE stmt FROM 'SELECT ? FROM employees';

-- 执行预处理语句，选择name列
EXECUTE stmt USING '@name';

-- 创建存储过程
DELIMITER //
CREATE PROCEDURE select_columns(IN column_name VARCHAR(50))
BEGIN
  SET @sql = CONCAT('SELECT ', column_name, ' FROM employees');
  PREPARE stmt FROM @sql;
  EXECUTE stmt;
  DEALLOCATE PREPARE stmt;
END //
DELIMITER ;

-- 调用存储过程，选择age列
CALL select_columns('age');