Fetching Columns of a multiple rows in one row

问题

I have a DB table with records as shown below,

ID   ATTR_NAME   ATTR_VALUE 
1    ABC          DEF
1    GHI          JKL
1    MNO          PQR

I would like to get a single row as

ID  ABC GHI  MNO
1   DEF JKL  PQR

回答1:

It may be a little fragile and not that future proofed, but Pivot can give you what you want:

SELECT *
FROM (
   SELECT attr_name, attr_value
   FROM   test
)
PIVOT
(  MIN(attr_value)
   FOR attr_name IN ( 'ABC','GHI','MNO' )
)

However, I'd advise that you consider if you really need it in that format and see if you can get it out in a more natural format.

回答2:

select ID, 
   sum(case when attr_name = 'ABC' then attr_value end) as ABC, 
   sum(case when attr_name = 'GHI' then attr_value end) as GHI, 
   sum(case when attr_name = 'MNO' then attr_value end) as MNO
from DB
group by ID;

来源：https://stackoverflow.com/questions/20568983/fetching-columns-of-a-multiple-rows-in-one-row