Question

I have two tables:

Unit:
UnitId int PK
Title varchar

UnitOption:
UnitOptionId int PK
UnitId int FK
Title varchar

Quote:
QuoteId int PK
UnitOptionId int FK
Title varchar

I want to create a scalar UDF that takes a QuoteId param and returns a varchar that contains the following description (pseudu):

Quote.Title + '-' + Unit.Title + '-' + Unit.UnitId + 
/* Here is where my question is:
If there are more than 1 UnitOption under this Unit, then
  return '-' + the UnitOption number under this Unit
  (i.e.) if under this Unit, there are 3 UnitOption with IDs 13, 17, 55
  under the unit, and the current Quote.UnitOptionId is the 17 one,
  it should return 2.
  Which means I want to retrieve an ID of this row in the group.
Else
  return ''
*/

Answer 1

CREATE FUNCTION ufnGetDescription 
  (@QuoteID INT) 
RETURNS VARCHAR(MAX) 
AS 
  BEGIN 
  DECLARE @RetVal VARCHAR(MAX); 

  WITH CurRow 
  AS (SELECT quote.title + '- ' + unit.title AS start, 
    u.unitid, 
    quoteid, 
    uo.unitoptionid 
  FROM quote 
    INNER JOIN unitoption uo 
    ON quote.unitoptionid = uo.unitoptionid 
    INNER JOIN unit 
    ON uo.unitid = unit.unitid 
  WHERE quote.quoteid = @QuoteID), 
  AllUnits 
  AS (SELECT u.unitid, 
    uo.unitoptionid, 
    Row_number() 
    OVER(PARTITION BY u.unitid ORDER BY uo.unitoptionid) AS NUMBER, 
    Count(* ) 
    OVER(PARTITION BY u.unitid )  AS cntUnits 
  FROM unit 
    INNER JOIN unionoption uo 
    ON unit.unitid = uo.unitid 
  WHERE u.unitid IN (SELECT unitid 
      FROM CurRow)) 
  SELECT @RetVal = CASE 
    WHEN a.cntUnits = 1 THEN '' 
    ELSE r.start + '-' + Cast(NUMBER AS VARCHAR(max)) 
    END 
  FROM AllUnits a 
  INNER JOIN CurRow r 
  ON a.unitoptionid = r.unitoptionid 

  RETURN @RetVal 
END