Question

我的表包含以下记录..表名：Cus1

Column:  c1 c2 c3 c4 c5 c6 c7 c8   c9  c10  c11  c12  c13  c14  c15

Records:  1  2  2  3  4  4  5  6    6    6    7    7    8    8    9 -1st record
          1  2  3  3  3  4  4  5    5    5    5    6    7    7    8 -2nd record

如何使用上表获得如下结果：

Column:  c1 c2 c3 c4 c5 c6 c7 c8   c9  c10  c11  c12  c13  c14  c15

Records:  1  2  3  4  5  6  7  8    9 NULL NULL NULL NULL NULL NULL -1st record
          1  2  3  4  5  6  7  8 NULL NULL NULL NULL NULL NULL NULL -2nd record

在DB2中使用if条件可能吗？

Answer 1

不知道“使用条件”是什么意思，但也许以下内容可能会引起关注？

设定：

create table cus1                                             
( c1  dec(3), c2  dec(3), c3  dec(3), c4  dec(3), c5  dec(3)  
, c6  dec(3), c7  dec(3), c8  dec(3), c9  dec(3), c10 dec(3)  
, c11 dec(3), c12 dec(3), c13 dec(3), c14 dec(3), c15 dec(3)  
) 
;
insert into  cus1  values                                     
  ( 1, 2, 2, 3, 4, 4, 5, 6,   6,   6,   7,   7,   8,   8,   9)
, ( 1, 2, 3, 3, 3, 4, 4, 5,   5,   5,   5,   6,   7,   7,   8)
;

使用来自设置的表数据来生成查询;每个在这里创建的VIEW将被查询以获得最终结果：

create view cus1_unpivot_view as                         
with                                                     
  cus1_rn as                                             
  ( select row_number() over() as rn                     
         , a.*                                           
    from cus1 a                                          
  )                                                      
SELECT rn, cn, cn_val                                    
FROM cus1_rn as C                                        
, lateral                                                
   ( values  (  1,  C.c1  ), (  6, C.c6  ), ( 11, C.c11 )
           , (  2,  C.c2  ), (  7, C.c7  ), ( 12, C.c12 )
           , (  3,  C.c3  ), (  8, C.c8  ), ( 13, C.c13 )
           , (  4,  C.c4  ), (  9, C.c9  ), ( 14, C.c14 )
           , (  5,  C.c5  ), ( 10, C.c10 ), ( 15, C.c15 )
   )  AS X( cn, cn_val )                                 
; /* create an unpivot view of columns to rows */
 create view cus1_unmatched as     
 select a.rn, a.cn, b.cn_val       
 from        cus1_unpivot_view as a
 left join                         
      ( select distinct rn, cn_val 
        from cus1_unpivot_view as d
      ) as b                       
    on a.rn=b.rn                   
   and a.cn=b.cn_val               
 ; /* Generate unmatched values to get NULL results */
create view cus1_pivot as                           
select rn                                           
     , max( case when cn=1  then cn_val end ) as c1 
     , max( case when cn=2  then cn_val end ) as c2 
     , max( case when cn=3  then cn_val end ) as c3 
     , max( case when cn=4  then cn_val end ) as c4 
     , max( case when cn=5  then cn_val end ) as c5 
     , max( case when cn=6  then cn_val end ) as c6 
     , max( case when cn=7  then cn_val end ) as c7 
     , max( case when cn=8  then cn_val end ) as c8 
     , max( case when cn=9  then cn_val end ) as c9 
     , max( case when cn=10 then cn_val end ) as c10
     , max( case when cn=11 then cn_val end ) as c11
     , max( case when cn=12 then cn_val end ) as c12
     , max( case when cn=13 then cn_val end ) as c13
     , max( case when cn=14 then cn_val end ) as c14
     , max( case when cn=15 then cn_val end ) as c15
from cus1_unmatched                                 
group by rn                                         
; /* pivot row data back to columns with the NULLs */

最后，查询最后一个VIEW以省略行编号并显示数据;将结果与期望的输出进行比较：

select
       c1  , c2  , c3  , c4  , c5  
     , c6  , c7  , c8  , c9  , c10 
     , c11 , c12 , c13 , c14 , c15 
from cus1_pivot
order by rn
; -- the following is a likeness of a report from the above query:
....+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8....+...
 C1    C2    C3    C4    C5    C6    C7    C8    C9   C10   C11   C12   C13   C14   C15 
  1     2     3     4     5     6     7     8     9      -     -     -     -     -     -
  1     2     3     4     5     6     7     8      -     -     -     -     -     -     -
********  End of data  ********

DB2使用if条件

1 个答案: