Subquery inside CASE statement

Question

I am trying to use a subquery within a Case statement with a 'where' condition that binds to the parent query. Like this:
Select T.idperson , CASE WHEN  T.type = 'C' THEN (SELECT name from Customers where C.idcustomer = T.idperson)
ELSE
(SELECT name from Providers where idprovider = T.idperson)
END Name
from myTable T This works for me in SQL Server but in ORACLE the subquery does not return any rows, i guess its the binding to parent query part. Any thoughts of another way I could get the result I want?
Thanks,
JuanDiego

Answer 1

Hi, Juandiego,
If it's not returning any rows, then you must not have any rows in the table.
If you have any rows in the table, you will either get
(a) an error, or
(b) some rows (even if the columns are NULL).
There is another way to get the results you want.
I probably wouldn't use scalar sub-queries. I would outer-join all the tables, like this:
Select  T.idperson
,       CASE
            WHEN  T.type = 'C'
            THEN  c.name
            ELSE  p.name
        END  AS Name
from             myTable   t
LEFT OUTER JOIN  Customers c  ON c.idcustomer = T.idperson
LEFT OUTER JOIN  Providers p  ON p.idprovider = T.idperson
;