MySql的日期函数

建表语句：
CREATE TABLE `orders` (
`orderid` int(11) NOT NULL AUTO_INCREMENT,
`product` varchar(20) DEFAULT NULL,
`count` int(11) DEFAULT NULL,
`orderdate` date DEFAULT NULL,
`name` varchar(20) DEFAULT NULL,
PRIMARY KEY (`orderid`)
) ENGINE=InnoDB AUTO_INCREMENT=41 DEFAULT CHARSET=latin1;

SELECT name, count(orderdate) count FROM orders group by orderdate;

添加数据：

insert into orders(product,count,orderdate,name) VALUES
('Hibernate2.5',10,date_format('20010815','%Y%m%d'),'qyf'),
('Struts2.0',10,date_format('20010915','%Y%m%d'),'qyf'),
('Spring2.0',10,date_format('20011015','%Y%m%d'),'qyf'),
('PHP 5.0',10,date_format('20050815','%Y%m%d'),'qyf'),
('PHP 4.0',10,date_format('20050805','%Y%m%d'),'qyf'),
('JavaScript',10,date_format('20101215','%Y%m%d'),'qyf'),
('C++',10,date_format('20100225','%Y%m%d'),'qyf'),
('C# 4.0',10,date_format('20101123','%Y%m%d'),'qyf'),
('VB++ .net',10,date_format('20101015','%Y%m%d'),'qyf'),
('JQuery',10,date_format(now(),'%Y%m%d'),'qyf'),
('XML book',10,date_format(now(),'%Y%m%d'),'qyf'),
('UML book',10,date_format(now(),'%Y%m%d'),'qyf'),
('JAVA ',10,date_format(now(),'%Y%m%d'),'qyf');

COMMIT

按年份查询用户所购买的图书：

SELECT name, year(orderdate), count(orderdate) count
FROM orders group by orderdate;

select date_format(now(),'%Y%m%d');