话不多说，直接上公式！ 

--   创建数据表
CREATE TABLE IF NOT EXISTS `mytable2`(
  `id` int  auto_increment primary key,
  `name` varchar(20) not null,
  `gender` varchar(20),
  `age` int,
  `brith` date );
	
-- 查询数据
select * FROM mytable2;
		
-- 查询数据的前四条
select * FROM mytable2 LIMIT 4;
		
-- where字句查询
select * from mytable2 where gender="女";

-- update 更改
update mytable2 set gender="undefined" where id=00010000004;

-- delete 删除
delete from mytable2 WHERE age<22;