使用IF ELSE语句重构存储过程

Question

In a webapp I'm working on there's a table which holds, so called, ProjectItems . The thing is that different types of project items reside in the same table; you could create a project, a question, an idea and a reaction. With a bitwise column the type is set in the [Type] column. And each project item could have a parent (defined by a column named fk_Parent ) in this same table.

The hierarchy is this:

Project (32) > Question (1) > Idea (2) > Reaction (4)

(I don't have any influence over the DB setup.)

I'm now creating a Stored Procedure for getting the root project item (of type Project) for any item with the ID passed as a parameter, but what I've got so far feels a little clunky:

CREATE PROC [dbo].[spProjectItemGetTopParentId]     
@ID INT

AS
    DECLARE @parentId INT
    SELECT @parentId =  fk_Parent FROM tblProjectItem WHERE ID = @ID
IF ((SELECT [Type] FROM tblProjectItem WHERE ID = @parentId) = 32)
    RETURN @parentId
ELSE
    SELECT @parentId =  fk_Parent FROM tblProjectItem WHERE ID = @parentId
IF ((SELECT [Type] FROM tblProjectItem WHERE ID = @parentId) = 32)
    RETURN @parentId
ELSE
    SELECT @parentId =  fk_Parent FROM tblProjectItem WHERE ID = @parentId
IF ((SELECT [Type] FROM tblProjectItem WHERE ID = @parentId) = 32)
    RETURN @parentId
ELSE
    SELECT @parentId =  fk_Parent FROM tblProjectItem WHERE ID = @parentId
IF ((SELECT [Type] FROM tblProjectItem WHERE ID = @parentId) = 32)
    RETURN @parentId
ELSE
RETURN 0
GO

I was wondering if there was any way to do this recursively in SQL? Or some other way to make this a little more neat?

EDIT: This is the SP including the a CTE:

CREATE PROC [dbo].[spTest]  
@ID INT

AS
DECLARE @parentId INT;
WITH Parents as (
    select ID,Type,fk_Parent from tblProjectItem where ID = @ID
    union all
    select pi.ID,pi.Type,pi.fk_Parent
    from
        Parents p
            inner join
        tblProjectItem pi
            on
                p.fk_Parent = pi.ID
)
select @parentId = ID from Parents where Type = 32

GO

Answer 1

Yes, a recursive CTE can find this for you:

;WITH Parents as (
    select ID,Type,parent_id from tblProjectItem where ID = @ID
    union all
    select pi.ID,pi.Type,pi.parent_id
    from
        Parents p
            inner join
        tblProjectItem pi
            on
                p.parent_id = pi.ID
)
select @parentId = ID from Parents where Type = 32

As a side note, I'd recommend against using prefixes for naming your database objects - with the exception of views and tables (that you should generally want to be indistinguishable) all object types can be clearly discerned by their usage - it's always clear from the position of a name in any particular query whether that name refers to a stored procedure, a (table|view), or a column, etc.

Answer 2

CREATE VIEW HierarchyExpanded AS 
BEGIN
    SELECT LVL1.ID      AS [LVL1ID]
          ,LVL1.[Type]  AS [LVL1Type]
          ,LVL2.ID      AS [LVL2ID]
          ,LVL2.[Type]  AS [LVL2Type]
          ,LVL3.ID      AS [LVL3ID]
          ,LVL3.[Type]  AS [LVL3Type]
          ,LVL4.ID      AS [LVL4ID]
          ,LVL4.[Type]  AS [LVL4Type]
    FROM   tblProjectItem LVL1
       INNER JOIN tblProjectItem LVL2
            ON  LVL2.fk_Parent = LVL1.ID
       INNER JOIN tblProjectItem LVL3
            ON  LVL3.fk_Parent = LVL2.ID
       INNER JOIN tblProjectItem LVL4
            ON  LVL4.fk_Parent = LVL3.ID
END



CREATE PROC [dbo].[spProjectItemGetTopParentId]     
@ID INT
AS
BEGIN
    DECLARE @parentId INT
    SELECT [LVL1ID]
    FROM   HierarchyExpanded
    WHERE  ([LVL1ID] =@ID 
    OR [LVL2ID] =@ID 
    OR [LVL3ID] =@ID 
    OR [LVL4ID] =@ID)
       AND [LVL1Type] = 32
END