Database

Case When size1 is null then 'S' else
   Case when size2 is null then 's1' else
      Case when size3 is null then 's2'
end end end as Size

CREATE PROC sp_MyProc (@ItemID AS INT)
AS
BEGIN
   SELECT *
   FROM   myTable
   WHERE  ItemID=isNull(@ItemID,ItemID)
END

SELECT *
FROM   myTable
WHERE  @ItemID IS NULL OR ItemId = @ItemId

IF @ItemID IS NULL 
BEGIN
   SELECT * FROM myTable; 
END
ELSE
BEGIN
   DECLARE @like NVARCHAR(6) 
   SET @like = '%' + CAST(@ItemID AS NVARCHAR(5))
   SELECT * FROM MyTable WHERE ItemID LIKE %like; 
END

ProjectId  ParentProject  ProjectName
1          0              X
2          1              Y
3          2              Z
4          3              W

SELECT PROJECTID,PROJECTNAME

FROM PROJECT 

WHERE PROJECTID = (	SELECT P1.PARENTPROJECTID + 1 
		FROM PROJECT P1
		INNER JOIN PROJECT P2
		ON P2.PROJECTID - <code>4</code>  = P1.PARENTPROJECTID )