Tabellvärderade UDF:er

Skriva funktioner och lagrade procedurer i SQL Server

Meghan Kwartler

IT Consultant

Inline-tabellvärderade funktioner (ITVF)

CREATE FUNCTION SumLocationStats (
  @StartDate AS datetime = '1/1/2017'
) RETURNS TABLE AS RETURN 
SELECT 
  PULocationID AS PickupLocation, 
  COUNT(ID) AS RideCount, 
  SUM(TripDistance) AS TotalTripDistance 
FROM YellowTripData 
WHERE CAST(PickupDate AS Date) = @StartDate 
GROUP BY PULocationID;

CREATE FUNCTION CountTripAvgFareDay (
  @Month char(2), 
  @Year char(4)
) RETURNS @TripCountAvgFare TABLE(
  DropOffDate date, TripCount int, AvgFare numeric
) AS BEGIN INSERT INTO @TripCountAvgFare 
SELECT 
  CAST(DropOffDate as date), 
  COUNT(ID), 
  AVG(FareAmount) as AvgFareAmt 
FROM YellowTripData 
WHERE 
  DATEPART(month, DropOffDate) = @Month 
  AND DATEPART(year, DropOffDate) = @Year 
GROUP BY CAST(DropOffDate as date)
RETURN END;

Skillnader – ITVF vs. MSTVF

Inline

RETURN returnerar resultatet av SELECT
Kolumnnamn definieras i SELECT
Ingen tabellvariabel
BEGIN END behövs inte
Ingen INSERT
Snabbare prestanda

Flerstegs

DECLARE en tabellvariabel som returneras
BEGIN END-block krävs
INSERT data i tabellvariabeln
RETURN som sista sats i BEGIN/END-blocket

Nu kör vi en övning!

Skriva funktioner och lagrade procedurer i SQL Server