问题来源：https://ask.csdn.net/questions/713436
参考答案：
测试表：
create table table1(id number,p1 number,p2 number,p3 number);
SQL> insert into table1 select 1,1,2,3 from dual;
1 row inserted
SQL> insert into table1 select 2,5,4,3 from dual;
1 row inserted
SQL> insert into table1 select 3,7,9,8 from dual;
1 row inserted
要求：
找出table1中每行最大的二列的列名
语法：
create view UNPIVOTview as
with UNPIVOTtable as (
SELECT id, DECODE(Puarter, 'P1', 'P1', 'P2', 'P2', 'P3', 'P3') AS Puarter, Puantity_sold
FROM Table1
UNPIVOT INCLUDE NULLS
(Puantity_sold
FOR Puarter IN (p1, p2, p3))
ORDER BY id)
select * from (
select id,Puantity_sold,Puarter,mod(rownum,3) rn from (
select id,Puantity_sold,Puarter from UNPIVOTtable order by id,Puantity_sold desc)
)
where rn between 1 and 2
;
SELECT id, listagg(PUARTER, ',') within group(order by id,PUANTITY_SOLD desc) pid
FROM UNPIVOTview
group by id;
效果：
SQL> select * from table1;
ID P1 P2 P3
---------- ---------- ---------- ----------
1 1 2 3
2 5 4 3
3 7 9 8
SQL> select * from UNPIVOTview;
ID PUANTITY_SOLD PUARTER RN
---------- ------------- ------- ----------
1 3 P3 1
1 2 P2 2
2 5 P1 1
2 4 P2 2
3 9 P2 1
3 8 P3 2
6 rows selected
SELECT id, listagg(PUARTER, ',') within group(order by id,PUANTITY_SOLD desc) pid
FROM UNPIVOTview
group by id;
ID PID
---------- --------------------------------------------------------------------------------
1 P3,P2
2 P1,P2
3 P2,P3