NVL in select query

Question

I have query as below
select a.id,
(select dep from table2 where table2.name=table1.name )
from table1
The second value is null as table2.name=table1.name has no value for table1
if i use NVL as below
select a.id,
(select NVL(dep,0) from table2 where table2.name=table1.name )
from table1
it is not fetching 0 in place of dep.Please help.I ned to use NVL here and show value 0 if the select returns null/blank

Answer 1

Hi,
It looks like you've got NVL in the wrong place. Try this:
SELECT  a.id
,     NVL ( ( SELECT  dep
             FROM      table2
          WHERE      table2.name     = table1.name
         , 0
         )     AS dep
FROM    table1
;If a scalar sub-query finds no rows, then it returns NULL, regarless of what is in the SELECT clause of the scalar sub-query.
You might want to avoid the scalar sub-query altogether, and use an outer join instead:
SELECT     a.id
,     NVL (b.dep, 0)     AS dep
FROM              table1  a
LEFT OUTER JOIN  table2  b  ON  a.name     = b.name
;I find this clearer and easier, and it might be more efficient, too.
Also, it won't raise an error if table2.name is not unique.
Edited by: Frank Kulash on Feb 1, 2011 12:43 PM