OLAP函数：之group by ()函数汇总之group by rollup()、group by cube()、grouping sets()

1.group by rollup(a,b,c) --group by (a,b,c), group by (a,b), group by (a), group by ()  的集合

2.group by cube(a,b,c) --group by (a,b,c), 

                       group by (a,b), group by (a,c), group by (b,c), 

                       group by (a), group by (b), group by(c)

                       group by ()  的集合

3.group by grouping sets(a,b,c) --group by (a), group by (b), group by (c) 的集合

其中，group by ()为对全表做汇总操作。

4.grouping() --GROUPING 表示GROUP BY 列表中的表达式是否参与分组，返回1 表示不参与分组，返回0 表示参与分组 。对普通GROUP BY表达式 ，GROUPING 返回0。

ROLLUP在数据统计和报表生成过程中带来极大的便利，而且效率比起来Group By + Union组合方法效率高得多。这也体现了Oracle在SQL统计分析上人性化、自动化、高效率的特点。

CUBE是ROLLUP的union集合数据。

--创建测试表group_test
create table group_test (group_id int, job varchar2(10), name varchar2(10), salary int);


--初始化数据
insert into group_test values (10,'Coding',    'Bruce',1000);
insert into group_test values (10,'Programmer','Clair',1000);
insert into group_test values (10,'Architect', 'Gideon',1000);
insert into group_test values (10,'Director',  'Hill',1000);

insert into group_test values (20,'Coding',    'Jason',2000);
insert into group_test values (20,'Programmer','Joey',2000);
insert into group_test values (20,'Architect', 'Martin',2000);
insert into group_test values (20,'Director',  'Michael',2000);

insert into group_test values (30,'Coding',    'Rebecca',3000);
insert into group_test values (30,'Programmer','Rex',3000);
insert into group_test values (30,'Architect', 'Richard',3000);
insert into group_test values (30,'Director',  'Sabrina',3000);

insert into group_test values (40,'Coding',    'Samuel',4000);
insert into group_test values (40,'Programmer','Susy',4000);
insert into group_test values (40,'Architect', 'Tina',4000);
insert into group_test values (40,'Director',  'Wendy',4000);

commit;

--ROLLUP()和CUBE()汇总一列时结果相同，如下：

select group_id,sum(salary) sums from group_test 
group by rollup(group_id)

select group_id,sum(salary) sums from group_test 

group by cube(group_id)

/*

ROLLUP()和CUBE()汇总多列时，ROLLUP()因字段顺序不同，结果不同。CUBE()于顺序无关。CUBE()是ROLLUP()对多个

字段每种情况排序的集合UNION。grouping()字段：如果显示“1”表示GROUPING函数对应的列（例如JOB字段）是由于ROLLUP函数所产生的空值对应的信息，即对此列进行汇总计算后的结果。 如果显示“0”表示此行对应的这列参未与ROLLUP函数分组汇总活动。

*/

select group_id,job,sum(salary) sums from group_test
group by rollup(group_id,job)


select group_id,job,sum(salary) sums from group_test
group by cube(job,group_id)


select group_id,job,sum(salary) sums from group_test

group by cube(group_id,job)

select group_id,job,grouping(GROUP_ID),grouping(JOB),sum(salary) from group_test group by rollup(group_id, job);

select 
nvl(job,'-1'),
nvl(deptno,'-1'),
sum(sal) ssal from emp 

group by grouping sets(job,deptno);

select 
nvl(job,'-1'),
nvl(deptno,'-1'),

sum(sal) ssal,

grouping(job),

grouping(deptno) from emp 

group by grouping sets(job,deptno);