【mysql】新增列 时间戳

参考地址：https://www.cnblogs.com/SZxiaochun/p/9299392.html

ALTER TABLE worksheet_data_12
 ADD COLUMN `input_0` VARCHAR (255),
 ADD COLUMN `date_112` TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

四种时间戳特性：

TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

TIMESTAMP DEFAULT CURRENT_TIMESTAMP

TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

TIMESTAMP DEFAULT 'yyyy-mm-dd hh:mm:ss' ON UPDATE CURRENT_TIMESTAMP