Pivoting in DB2

Question

I have to transpose my rows into columns from a DB2 table.This is how my table is structured..

ItemID    Item    Value
---------------------
1     Meeting     Now
1     Advise      Yes
1     NoAdvise    No
2     Meeting     Never
2     Advise      No
2     NoAdvise    Null
2     Combine    Yes

I want this to be transposed into(note that I do not want to transpose Combine)

ItemID    Meeting  Advise   NoAdvise 
---------------------------------------
1         Now      Yes       No
2         Never    No        Null

Bit struggling with the query, can you please help?

Answer 1

The currently accepted answer by bhamby is certainly correct, but it's worth checking if using several correlated subqueries is much slower than a single group by (hint: it most likely is):

SELECT 
  A.ItemID,
  MAX(CASE WHEN A.Item = 'Meeting'  THEN Value END) AS Meeting,
  MAX(CASE WHEN A.Item = 'Advise'   THEN Value END) AS Advise,
  MAX(CASE WHEN A.Item = 'NoAdvise' THEN Value END) AS NoAdvise
FROM A
GROUP BY A.ItemID

It's also a bit simpler in my opinion

SQLFiddle (in PostgreSQL, but works on DB2 LUW as well)

Answer 2

It's not very pretty, but it should work. DB2 doesn't have a built-in PIVOT function, like SQL Server.

SELECT DISTINCT
     A.ItemID
    ,(SELECT value
      FROM table B
      WHERE B.ItemID = A.ItemID
        AND B.Item   = 'Meeting'
    ) AS Meeting
    ,(SELECT value
      FROM table B
      WHERE B.ItemID = A.ItemID
        AND B.Item   = 'Advise'
    ) AS Advise
    ,(SELECT value
      FROM table B
      WHERE B.ItemID = A.ItemID
        AND B.Item   = 'NoAdvise'
    ) AS NoAdvise
FROM table A