一个关于Decode( )转换数据视图的问题

Question

select
CLAIM_YEAR month_year,
max(decode(CLAIM_CLASS,'01', CLAIM_CHARGE,null)) rent1,
max(decode(CLAIM_CLASS,'02', CLAIM_CHARGE,null)) rent2,
max(decode(CLAIM_CLASS,'03', CLAIM_CHARGE,null)) rent3
from
T_CLAIM_CHARGE_DETAIL
group by 
         CLAIM_YEAR

Answer 1

试试下面：
select
CLAIM_YEAR month_year,
max(decode(CLAIM_CLASS,'01', CLAIM_CHARGE,null)) rent1,
max(decode(CLAIM_CLASS,'02', CLAIM_CHARGE,null)) rent2,
max(decode(CLAIM_CLASS,'03', CLAIM_CHARGE,null)) rent3
from
T_CLAIM_CHARGE_DETAIL group by CLAIM_YEAR month_year;

Answer 2

改一下：
select
CLAIM_YEAR month_year,
max(decode(CLAIM_CLASS,'01', CLAIM_CHARGE,null)) rent1,
max(decode(CLAIM_CLASS,'02', CLAIM_CHARGE,null)) rent2,
max(decode(CLAIM_CLASS,'03', CLAIM_CHARGE,null)) rent3
from
T_CLAIM_CHARGE_DETAIL group by CLAIM_YEAR

Answer 3

SELECT month_year,
max(RENT1) RENT1,
max(RENT2) RENT2,
max(RENT3) RENT3
FROM
(
SELECT CLAIM_YEAR month_year,
CLAIN_CHARGE RENT1,
'' RENT2,
'' RENT3
WHERE CLAIM_CLASS = '01'
UNION ALL
SELECT CLAIM_YEAR month_year,
'' RENT1,
CLAIN_CHARGE  RENT2,
'' RENT3
WHERE CLAIM_CLASS = '03'
UNION ALL
SELECT CLAIM_YEAR month_year,
'' RENT1,
'' RENT2,
CLAIN_CHARGE RENT3
WHERE CLAIM_CLASS = '03'
)
GROUP BY month_year

Answer 4

重新发一下，刚才的有点问题SELECT month_year,
max(RENT1) RENT1,
max(RENT2) RENT2,
max(RENT3) RENT3
FROM
(
SELECT CLAIM_YEAR month_year,
CLAIN_CHARGE RENT1,
'' RENT2,
'' RENT3
WHERE CLAIM_CLASS = '01'
UNION ALL
SELECT CLAIM_YEAR month_year,
'' RENT1,
CLAIN_CHARGE  RENT2,
'' RENT3
WHERE CLAIM_CLASS = '02'
UNION ALL
SELECT CLAIM_YEAR month_year,
'' RENT1,
'' RENT2,
CLAIN_CHARGE RENT3
WHERE CLAIM_CLASS = '03'
)
GROUP BY month_year