Mysql8 DDL常用sql

常用DDL语句

`create_by` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL DEFAULT 'system' COMMENT '创建人',
`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
`update_by` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL DEFAULT 'system' COMMENT '更新人',
`update_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',
`version` int NOT NULL DEFAULT '1' COMMENT '乐观锁，默认值1',