group by 字句的扩展+rollup字句+cube字句+grouping（）函数

1rollup字句 rollup字句扩展group by字句，为每一个分组返回一条小计记录，并为全部分组返回总计 列如：rollup字句获取每个部门的工资总计 select d.dname,sum(e.sal) from emp e,dept d where e.deptno=d.deptno group by rollup(d.dname) order by d.dname; 解释： dname

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