无法在Oracle PIVOT子句中使用用户定义的聚合函数.
我创建了一个名为string_agg的用户定义聚合函数.
我可以在一个简单的声明中使用它,例如……
select id,string_agg(value) from
(
select 'user1' as id,'BMW' as value,'CAR' as type from dual union
select 'user1' as id,'Audi' as value,'CAR' as type from dual union
select 'user2' as id,'Honda' as value,'Dell' as value,'COMPUTER' as type from dual union
select 'user1' as id,'Sony' as value,'COMPUTER' as type from dual union
select 'user2' as id,'HP' as value,'COMPUTER' as type from dual
)
group by id,type
结果是：
ID TYPE STRING_AGG(VALUE) user1 CAR Audi,BMW user1 COMPUTER Dell,Sony user2 CAR Honda user2 COMPUTER HP
但是当我尝试在pivot子句中使用相同的函数时
select * from
(
select id,type,string_agg(value) as value from
(
select 'user1' as id,'CAR' as type from dual union
select 'user1' as id,'CAR' as type from dual union
select 'user2' as id,'COMPUTER' as type from dual union
select 'user1' as id,'COMPUTER' as type from dual union
select 'user2' as id,'COMPUTER' as type from dual
)
group by id,type
)
PIVOT (string_agg(value) FOR id IN ('user1' user1,'user2' user2) );
我收到以下错误…
ORA-56902: expect aggregate function inside pivot operation
预期结果是……
TYPE USER1 USER2 COMPUTER Dell,Sony HP CAR Audi,BMW Honda
解决方法
Pivot不必超过相同的聚合函数：
select * from
(
select id,LISTAGG(value) WITHIN GROUP (ORDER BY 1) as value from
(
select 'user1' as id,type
)
PIVOT (max(value) FOR id IN ('user1' user1,'user2' user2) );
