Nvl question (kind off)

Question

Hi guys,
I was wondering if you could help me out please.
I have a table with a start_date and end_date as well as a temp_start_date and temp_end_date column.
What I want to do is display the start_date and end_date BUT, if the start_date is null I want to show the temp_start_date and temp_end_date in that column.
I was thinking I could use nvl or possibly decode to do this?
The first bit I think is straight forward, I nvl the start_date to the temp_start_date, but im not sure how to proceed from there? I only want to show the temp_end_date if the start_date is null. Any help on this would be greatly appreciated.
Select nvl(start_date,temp_start_date), end_date
From my_table
Thanks

Answer 1

Hi,
Use the NVL<b>2</b> function for that
SELECT     NVL ( start_date
         , temp_start_date
         )          AS s_date
,     NVL2 ( start_date
          , end_date
          , temp_end_date
          )             AS e_date
FROM    table_x
;You could use DECODE or CASE to test if start_date is NULL, and, depending on the answer, return either end_date or temp_end_date, but NVL2 was designed specifcally to do that. That is, the NVL2 expression above is equivalent to
,     CASE
         WHEN  start_date  IS NOT NULL
         THEN  end_date
         ELSE  temp_end_date
     END             AS e_dateand also
,     DECODE ( start_date
            , NULL     , temp_end_date
                       , end_date
            )        AS e_date 
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
Explain, using specific examples, how you get those results from that data.
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