Code bellow is not working, any ideas why?
declare @Counter int
set @Counter = 0
declare @ConcText nvarchar(1000)
while @Counter < 5
begin
--set @ConcText = @ConcText + cast(@Counter as nvarchar(10)) + N' counter,'
--set @ConcText = @ConcText + convert(nvarchar(10), @Counter) + N' counter,'
set @ConcText = @ConcText + N' counter,'
set @Counter = @Counter + 1
end
print @ConcText --<-- this is null, why ??
See MSDN: + (String Concatenation) (Transact-SQL):
Just like arithmetic operations that are performed on null values, when a null value is added to a known value the result is typically an unknown value, a string concatenation operation that is performed with a null value should also produce a null result.
So to get things work, it's a good practice to initiate varchar variables immediatly after declare:
DECLARE @ConcText NVARCHAR(1000)
SET @ConcText = ''
Other way to handle NULL concat issue (in case you don't know if value is NULL or not) - ISNULL or COALESCE:
SET @ConcText = ISNULL(@ConcText, '') + N' counter,'
SET @ConcText = COALESCE(@ConcText, '') + N' counter,'
You are not setting @ConcText to anything at the start, therefore when you concatenate anything to NULL you get NULL.
