1delete from dz where 年级='2006'2select jc.书名,dz.姓名,jc.借出日期+jc.期限 as 归还日期 from dz,jc where dz.借书证号=jc.借书证号
and jc.借出日期+jc.期限='2011-6-30' 3 select dz.年级,count(*) as 借书数量 from dz,jc where dz.借书证号=jc.借书证号 group by dz.年级
1delete from dz where 年级='2006'2select jc.书名,dz.姓名,jc.借出日期+jc.期限 as 归还日期 from dz,jc where dz.借书证号=jc.借书证号
and jc.借出日期+jc.期限='2011-6-30' 3 select dz.年级,count(*) as 借书数量 from dz,jc where dz.借书证号=jc.借书证号 group by dz.年级