mysql跨年按周分组_MySQL

Sql代码  use employees;  create table sales(      id int auto_increment,      date datetime not null,      cost int unsigned not null,      primary key(id)  );    insert into sales (date,cost)values('2010-12-31',100);  insert into sales (date,cost)values('2011-01-01',200);  insert into sales (date,cost)values('2011-01-02',100);  insert into sales (date,cost)values('2011-01-06',100);  insert into sales (date,cost)values('2011-01-10',100);    SELECT * FROM employees.sales;    select week(date),sum(cost)from sales group by week(date);    select floor(datediff(date,'1900-01-01')/7) as a,sum(cost) from sales group by floor(datediff(date,'1900-01-01')/7);    /*最终解决方案*/  select date_add('1900-01-01',interval floor(datediff(date,'1900-01-01')/7)*7 day) as week_start,  date_add('1900-01-01',interval floor(datediff(date,'1900-01-01')/7)*7+6 day)as week_end,sum(cost) from sales  group by floor(datediff(date,'1900-01-01')/7);