高分请教 一句sql

Question

SELECT PEOPLE,
   SUM(DECODE("TYPE",'A',AMOUNT,0)) AS A,
   SUM(DECODE("TYPE",'B',AMOUNT,0)) AS B,
   SUM(DECODE("TYPE",'C',AMOUNT,0)) AS C,
   SUM(DECODE("TYPE",'D',AMOUNT,0)) AS D
FROM T
GROUP BY PEOPLE

Answer 1

13:15:24 SQL*PLUS>select * from bb;PEOPLE     TYPE                     AMOUNT
---------- -------------------- ----------
ad         a                           234
ad         b                           345
ad         a                           234
ch         c                            43
ch         d                           435
an         a                           435已选择6行。已用时间:  00: 00: 00.00
13:15:29 SQL*PLUS>SELECT people ,SUM(decode(TYPE,'a',0,amount)) a,
13:15:30   2  SUM(decode(TYPE,'b',0,amount)) b,
13:15:30   3  SUM(decode(TYPE,'c',0,amount)) c,
13:15:30   4  SUM(decode(TYPE,'d',0,amount)) d
13:15:30   5  FROM bb GROUP BY people;PEOPLE              A          B          C          D
---------- ---------- ---------- ---------- ----------
ad                345        468        813        813
an                  0        435        435        435
ch                478        478        435         43已用时间:  00: 00: 00.00
13:15:31 SQL*PLUS>

Answer 2

SELECT 
    people,
    MAX(DECODE(type ,'A' ,amount ,0)) AS A,
    MAX(DECODE(type ,'B' ,amount ,0)) AS B,
    MAX(DECODE(type ,'C' ,amount ,0)) AS C,
    MAX(DECODE(type ,'D' ,amount ,0)) AS D
FROM 
    tabname
GROUP BY 
    people

Answer 3

上面把反了
13:15:31 SQL*PLUS>SELECT people ,SUM(decode(TYPE,'a',amount,0)) a,
13:18:20   2  SUM(decode(TYPE,'b',amount,0)) b,
13:18:20   3  SUM(decode(TYPE,'c',amount,0)) c,
13:18:20   4  SUM(decode(TYPE,'d',amount,0)) d
13:18:20   5  FROM bb GROUP BY people;PEOPLE              A          B          C          D
---------- ---------- ---------- ---------- ----------
ad                468        345          0          0
an                435          0          0          0
ch                  0          0         43        435已用时间:  00: 00: 00.00
13:18:21 SQL*PLUS>

Answer 4

select people,
       sum(decode(type,'A',amount,0)) A,
       sum(decode(type,'B',amount,0)) B,
       sum(decode(type,'C',amount,0)) C,
       sum(decode(type,'D',amount,0)) D
from tbl
group by people;

Answer 5

select people,
       max(decode(type, 'A', amount, 0)) A,
       max(decode(type, 'B', amount, 0)) B,
       max(decode(type, 'C', amount, 0)) C,
       max(decode(type, 'D', amount, 0)) D
  from tablename
 group by people