Question

I have a table which has a list which looks like this

References

R. Name    LineNo.       References
  A         1.1           (B,24.1)
  A         6.3           (A, 1.3), (D, 22.1)
  B         23.1          (A. 1.2)
  B         24.1          (B,23.1)
  C         2             (A, 1.1)
  D         3.12          (A, 6.3)

The query should go one by one in the records and generate a value based on the references, pick first one lets say, which is Report Name A, Line No. 1.1, Now the reference is (B, 24.1), which means we need to find Report Name B, line no 24.1 and pick its value. In the same table R.Name B and Line No B, 24.1 is referenced by (B, 23.1), So now we need to find Report name B, Line No 23.1, We go on through the iteration unless we cant find a reference in the same table, which means the last one we cant find has a value in another table. (Only References without values are found in this table) ...Look at the table below

Table: GeneratedValues

R.Name  LineNo.    Values
----------------------------------------
A       1.2          5632
A       1.3          12.5
A       2.1          25
A       2.2          121
A       2.3          8

Now A, 1.1 References B, 24.1 Which references B, 23.1 Which references A, 1.2 And Since A, 1.2 doesnt exist in the reference table another query runs and fetches the number from the Generated Values table. In this case 5632, Hence A, 1.1 = 5632.

Like this we go one by one through each record.

My problem is i dont know how to write a recursive query to implement this.

Hussain

Answer 1

Let s break it down.

Firstly, a UDF to get the next value

CREATE FUNCTION dbo.GetNextReference
(
    @CurrentRef varchar(25)
)
RETURNS varchar(25)
AS
BEGIN
    DECLARE @NextRef varchar(25)
    SELECT @NextRef = [References]
    FROM R
    WHERE  (  + [Name] +  ,  + [LineNo] +  )  = @CurrentRef

    RETURN @NextRef
END

Next one to find the final value for each entry :

CREATE FUNCTION dbo.GetFinalReference
(
    @StartRef varchar(25)
)
RETURNS varchar(25)
AS
BEGIN
    DECLARE @NextRef varchar(25), @CurrentRef varchar(25)
    SELECT @NextRef = dbo.GetNextReference(@StartRef), @CurrentRef = @StartRef
    WHILE @NextRef is not null
    BEGIN
        SET @CurrentRef = @NextRef
        SET @NextRef = dbo.GetNextReference(@CurrentRef)
    END

    --at this point @NextRef will be null, so we look in the other table
    DECLARE @FinalValue varchar(25)
    SELECT @FinalValue = [Values]
    FROM GeneratedValues
    WHERE  (  + [Name] +  ,  + [LineNo] +  )  = @CurrentRef

    RETURN @FinalValue
END

Finally, we can run a SELECT

SELECT [Name], [LineNo], dbo.GetFinalReference([References]) AS [Values]
FROM R

I hope this is all clear, and I haven t made any syntactical errors. The use of UDFs may mean this query won t run as quick as you d like, but I think the UDFs will be useful to you in any case.

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