database - Oracle PIVOT 子句中的用户定义聚合函数

Question

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。
我可以在简单的语句中使用它，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, 'CAR'      as type from dual    union
    select 'user1' as id, '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:

<b>ID          TYPE            STRING_AGG(VALUE)</b>
user1       CAR             Audi,BMW
user1       COMPUTER        Dell,Sony
user2       CAR             Honda
user2       COMPUTER        HP

但是，当我尝试在数据透视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, '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, 'CAR'      as type from dual    union
        select 'user1' as id, '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
)
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<br/>

预期 结果是...

<b>TYPE        USER1       USER2</b>
COMPUTER    Dell,Sony   HP       
CAR         Audi,BMW    Honda

Answer 1

Pivot 不必在同一个聚合函数上:

select * from
( 
    select id, type, LISTAGG(value) WITHIN GROUP (ORDER BY 1) as 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, 'CAR'      as type from dual    union
        select 'user1' as id, '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
)
PIVOT (max(value) FOR id IN ('user1' user1, 'user2' user2) );