Flexible select query

Question

I know that comparison operators don't work with null values in SQL so for that we use isnull, Now I have a situation with a table like this,

ID      Name        Order
3   KnowledgeBase1  NULL
4   KnowledgeBase2  NULL
5   KnowledgeBase3  NULL
6   KnowledgeBase4  NULL
7   Child of first  1

Now here you can see that Order can be null or any numeric value,

Now here's the select query

declare @order int = null

select 
        ID,
        Name,
        Order
from tbl
where Order = @order

this query is good when @order has any numerals but when it has null it doesn't work of course because where clause should be Order is null for that case,

So question is that is there any way to do this without using exec() with a string of query or a conditional statement in my query ??

Answer 1

Compare @order to NULL in the where clause, and if it is, use order IS NULL and OR that together with your existing condition that works if it has a value:

select 
        ID,
        Name,
        Order
from tbl
where 
  Order = @order
  OR (@order IS NULL AND order IS NULL)

You have not specified your RDBMS, but a quick test shows this working with MySQL...