First record in SQL Cursor missing a variable - sql-server

Question

I am sending a newsletter in SQL server using a cursor. All is working fine except the first email has no html.
Here is the stored procedure:.....
DECLARE
#html varchar(max)
SET #html = (SELECT html from NewsLetter where nLID=#nLID)
DECLARE crsEmailList CURSOR FOR
SELECT email, ListID from lists where category=#Category AND (DLC < DATEADD(DAY, -1,GETDATE()) OR DLC IS NULL)
OPEN crsEmailList
FETCH NEXT FROM crsEmailList INTO #email, #ListID
while ##FETCH_STATUS = 0
BEGIN
DECLARE #UniqueKey varchar(20),
#UnSubscribeURL varchar(200),
#ClickURL varchar(200)
SET #UnSubscribeURL='<a href=''http://.../userfiles/OHP/UnSubscribe.aspx?listID=' + convert(varchar, #ListID) + '''>Unsubscribe</a>'
SET #ClickURL='<a href=''http://.../userfiles/OHP/clicked.aspx?Key=' + convert(varchar, #UniqueKey ) + '&URL='
EXEC [register_system_email_audits] #ListID, #email, #Date, #UniqueKey output
SET #html = (SELECT html from NewsLetter where nLID=#nLID)
SET #html = Replace(#html,'[keyvalue]', #UniqueKey)
SET #html = Replace(#html,'<a href=\''',#ClickURL)
SET #html = Replace(#html,'[UnSubscribe]', #UnSubscribeURL )
SET #html = Replace(#html,'[date]', DATENAME(month, getdate()) )
EXEC msdb.dbo.sp_send_dbmail
#profile_Name ='Local Server',
#recipients= #email ,
#subject = #Subject,
#body = #html,
#body_format='HTML'
FETCH NEXT FROM crsEmailList INTO #email, #ListID
END
I have tried moving the line SET #html = (SELECT html from NewsLetter where nLID=#nLID) to different locations but no positive results.

Answer 1

One very likely explanation is that one of the parameters you are plugging into the html string is NULL for the first iteration.
When I run this code:
DECLARE #Str varchar(max) = 'Hello [test]';
DECLARE #test varchar(max) = NULL;
SET #Str = REPLACE(#Str, '[test]', #test);
PRINT #Str;
I don't get 'Hello ' as a result. I get nothing. So apparently using REPLACE to plug a NULL value into a string has the same effect as concatenating the string with NULL: which is, it makes the whole thing NULL.
Try using ISNULL on each of the variables in your REPLACE statements, and see if that doesn't fix the problem.
SET #html = Replace(#html,'[keyvalue]', ISNULL(#UniqueKey,''))
Or alternately, do the NULL-handling further upstream in the proc, but make sure you can't be trying to replace a token with NULL.