question

If the variable named @extra_value is null then the whole @query_string is set to null due to **concat\_nulls\_yields\_null** setting. Also, you assume that the variable is a string, but this is not necessarily so because it could be something else which does not require single quotes around it. In fact, if the value is null then you want the resulting SQL to read ***set SomeColumn = null*** rather than ***set SomeColumn = 'null'***. To prevent unexpected results, just modify this variable and the script like this: if the value is null then just spell out null (no single quotes), otherwise, add single quotes around the value. If the variable has any single quotes as a part of its value then every occurrence of the single quote must be replaced with 2 single quotes in order not to break the resulting dynamic script. In any case, remove the extra single quotes (which are not needed with this approach) from around the variable setting part of the @query_string. Here is the script which will work regardless of whether the variable named @extra_value is null or not, and has any single quotes as a part of it's value: select @extra_value = case when @extra_value is null then 'null' else '''' + replace(@extra_value, '''', '''''') + '''' end; declare @query_string nvarchar(max) = ' update c set c.' + @extra_type + ' = ' + cast(@extra_value as nvarchar(max)) + ' from ws_user_flat_t_'+ cast(@Companyid as varchar(20)) + ' c inner join #inserted i on i.reward_user_id = c.id where c.id = '+ cast(@user_id as varchar(20)) + ' ' print @query_string; --execute sp_executesql @query_string; Hope this helps, Oleg