函数---GROUPING
GROUPINGGROUPING函数可以接受一列，返回0或者1。如果列值为空，那么GROUPING()返回1；如果列值非空，那么返回0。GROUPING只能在使用ROLLUP或CUBE的查询中使用。当需要在返回空值的地方显示某个值时，GROUPING()就非常有用。1、在ROLLUP中对单列使用GROUPING()SQL> select division_id,sum(salary) 2 from employees2 3 group by rollup(division_id) 4 order by division_id;DIV SUM(SALARY)--- -----------BUS 1610000OPE 1320000SAL 4936000SUP 1015000 8881000加上GROUPING来看看SQL> select grouping(division_id),division_id,sum(salary) 2 from employees2 3 group by rollup(division_id) 4 order by division_id;GROUPING(DIVISION_ID) DIV SUM(SALARY)--------------------- --- ----------- 0 BUS 1610000 0 OPE 1320000 0 SAL 4936000 0 SUP 1015000 1 8881000可以看到，为空的地方返回1，非空的地方返回0。2、使用CASE转换GROUPING()的返回值可能你会觉得前面的0和1太枯燥了，代表不了任何意义，说白了就是不够人性化，呵呵。这个时候我们可以使用CASE来转换为一些有意义的值。SQL> select 2 case grouping(division_id) 3 when 1 then 'all divisions' 4 else division_id 5 end as div, 6 sum(salary) 7 from employees2 8 group by rollup(division_id) 9 order by division_id;DIV SUM(SALARY)------------- -----------BUS 1610000OPE 1320000SAL 4936000SUP 1015000all divisions 88810003、使用CASE和GROUPING()转换多个列的值SQL> select 2 case grouping(division_id) 3 when 1 then 'all divisions' 4 else division_id 5 end as div, 6 case grouping(job_id) 7 when 1 then 'all jobs' 8 else job_id 9 end as job, 10 sum(salary) 11 from employees2 12 group by rollup(division_id,job_id) 13 order by division_id,job_id;DIV JOB SUM(SALARY)------------- -------- -----------BUS MGR 530000BUS PRE 800000BUS WOR 280000BUS all jobs 1610000OPE ENG 245000OPE MGR 805000OPE WOR 270000OPE all jobs 1320000SAL MGR 4446000SAL WOR 490000SAL all jobs 4936000DIV JOB SUM(SALARY)------------- -------- -----------SUP MGR 465000SUP TEC 115000SUP WOR 435000SUP all jobs 1015000all divisions all jobs 888100016 rows selected.4、CUBE与GROUPING()结合使用SQL> select 2 case grouping(division_id) 3 when 1 then 'all divisions' 4 else division_id 5 end as div, 6 case grouping(job_id) 7 when 1 then 'all jobs' 8 else job_id 9 end as job, 10 sum(salary) 11 from employees2 12 group by cube(division_id,job_id) 13 order by division_id,job_id;DIV JOB SUM(SALARY)------------- -------- -----------BUS MGR 530000BUS PRE 800000BUS WOR 280000BUS all jobs 1610000OPE ENG 245000OPE MGR 805000OPE WOR 270000OPE all jobs 1320000SAL MGR 4446000SAL WOR 490000SAL all jobs 4936000DIV JOB SUM(SALARY)------------- -------- -----------SUP MGR 465000SUP TEC 115000SUP WOR 435000SUP all jobs 1015000all divisions ENG 245000all divisions MGR 6246000all divisions PRE 800000all divisions TEC 115000all divisions WOR 1475000all divisions all jobs 888100021 rows selected.5、使用GROUPING SETS子句使用GROUPING SETS子句可以只返回小计记录。SQL> select division_id,job_id,sum(salary) 2 from employees2 3 group by grouping sets(division_id,job_id) 4 order by division_id,job_id;DIV JOB SUM(SALARY)--- --- -----------BUS 1610000OPE 1320000SAL 4936000SUP 1015000 ENG 245000 MGR 6246000 PRE 800000 TEC 115000 WOR 14750009 rows selected.
