informix 求行的最值

Question

原表T
a b c d e
1 2 4 5 9
1 2 8 4 5
3 3 2 5 6想求出每一行的最值，即
a b c d e max
1 2 4 5 9 9
1 2 8 4 5 8
3 3 2 5 6 6哪位大侠给出出招啊，我想到的方法
1：行列转置，然后用max函数求，再转置回去
2：用perl，将表数据导出给数组，取出每行的最值，再入会库中
大侠们给解决下吧

Answer 1

select t.*,greatest(a,b,c,d,e) maxval
from t

Answer 2

这个greatest是什么东西？我在informix里执行报错误啊，
Routine (greatest) can not be resolved
你的能执行？

Answer 3

我写了个perl将数据取出，算出每行的最值，在入回表里了！！

Answer 4

update T
   set t.max=t.a;
update t
   set t.max=decode(max>b,max,b);
update t
   set t.max=decode(max>c,max,c);
update t
   set t.max=decode(max>d,max,d);
update t
   set t.max=decode(max>e,max,e);

Answer 5

SQL> select * from t;
 
                    A                     B                     C                     D                     E                   MAX
--------------------- --------------------- --------------------- --------------------- --------------------- ---------------------
                    1                    12                     3                     2                    12 
                    3                    23                     5                     3                     6 
                   32                    64                     6                     8                    32 
                   23                    66                    87                    34                    23 
 
SQL> 
SQL> update T
  2    set t.max=t.a;
 
4 rows updated
SQL> update t
  2    set t.max=decode(sign(t.max-b),1,t.max,b);
 
4 rows updated
SQL> update t
  2    set t.max=decode(sign(t.max-c),1,t.max,c);
 
4 rows updated
SQL> update t
  2    set t.max=decode(sign(t.max-d),1,t.max,d);
 
4 rows updated
SQL> update t
  2    set t.max=decode(sign(t.max-e),1,t.max,e);
 
4 rows updated
SQL> SELECT * FROM t;
 
                    A                     B                     C                     D                     E                   MAX
--------------------- --------------------- --------------------- --------------------- --------------------- ---------------------
                    1                    12                     3                     2                    12                    12
                    3                    23                     5                     3                     6                    23
                   32                    64                     6                     8                    32                    64
                   23                    66                    87                    34                    23                    87
 
SQL>