How to get the null values in my stored procedure i am getting error dbnullvalue on front

I have the following stored proc. which i am using on the front end to get all the record from table:

if there are any fields it has anynull values in it i am getting error dbnull value error.
i have null value for ReviewerComment field, can you please tell me how to pass a "" if it is null, in the store proc only, to get all the fresh dat to front end before bnding it to the datagrid control.

CREATE PROCEDURE [dbo].[sp_displayrevws]
AS
select r.RevID,
rtrim(f.revwfunction) as revwfunction,
rtrim(u.uname) as uname,
CONVERT(varchar(10),r.Issued,101) as Issued,
r.ReviewerComment,
r.Response,
r.ModuleID,
rtrim(r.ModuleName) as modulename,
r.ReviewerUserID,r.RevFunctionid,r.Dispositionid
from TAB_ccsNetReviewers r, tabuname u, ccsfunctions f, ccsdisposition d where u.id = r.ReviewerUserID and r.RevFunctionid = f.id and r.Dispositionid = d.id and r.ModuleID = 1 order by r.RevID ASC
GO

Thank you very much.Note use of IsNull() function.

CREATE PROCEDURE [dbo].[sp_displayrevws]
AS
select r.RevID,
rtrim(f.revwfunction) as revwfunction,
rtrim(u.uname) as uname,
CONVERT(varchar(10),r.Issued,101) as Issued,
IsNull(r.ReviewerComment,''),
r.Response,
r.ModuleID,
rtrim(r.ModuleName) as modulename,
r.ReviewerUserID,r.RevFunctionid,r.Dispositionid
from TAB_ccsNetReviewers r, tabuname u, ccsfunctions f, ccsdisposition d where u.id = r.ReviewerUserID and r.RevFunctionid = f.id and r.Dispositionid = d.id and r.ModuleID = 1 order by r.RevID ASC
GO

|||You can use the case statement in sql to look at a field before its returned. For example, you could do this (uses the pubs db)

select au_lname, au_fname,
AuthorCity = Case when (city is null) then '' else city end
from authors

if any city values are null, they'll come back as a '' empty string.

Hope this helps,

Scott