Conditional Sql Query

From http://stackoverflow.com/questions/2235889/conditional-sql-query

CREATE PROCEDURE [dbo].[GetRecentlyListedProperties]
(@location varchar(100), @city varchar(100),@propertyID int)
As
Begin
DECLARE @numberOfDays int,
        @propertyCount int,
        @IsLocation bit -- looking for a location and not a city
SET @Propertycount = 0
SET @numberOfDays= 10
-- CHECK TO SEE IF THERE ARE LISTINGS IN THE LAST 10 DAYS IN THE SAME LOCATION
SELECT  @PropertyCount =
 Count(*) FROM properties where location = @location and DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
 and PropertyID != @propertyID
If(@PropertyCount = 0)
Begin
-- CHECK TO SEE IF THERE ARE LISTINGS IN THE LAST 10 DAYS IN THE SAME CITY
SELECT  @PropertyCount = Count(*) from properties where city = @city
        AND DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
        AND PropertyID != @propertyID
    IF(@PropertyCount = 0 )
    BEGIN
    SET @NumberOfDays = 30
    -- CHECK TO SEE IF THERE ARE LISTINGS IN THE LAST 30 DAYS IN THE SAME LOCATION
    SELECT  @PropertyCount = COUNT(*) from properties where location = @location
            AND DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
            AND PropertyID != @propertyID
        IF(@PropertyCount = 0 )
        BEGIN
        -- CHECK TO SEE IF THERE ARE LISTINGS IN THE LAST 30 DAYS IN THE SAME CITY
        SELECT @PropertyCount = Count(*) from properties where city = @city
                AND DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
                AND PropertyID != @propertyID
        END
        ELSE
        SET @IsLocation = 1 --There are properties in the same location in the last 30 days
    END
    ELSE
    SET @IsLocation  = 0 -- There are properties listed int he city in the last 10 days
End
Else
SET @IsLocation = 1
-- This is where the appropriate results are returned.
IF(@IsLocation = 1)
Begin
SELECT * ,(SELECT AVG(PRICE) as AveragePrice
       FROM PROPERTIES
       WHERE DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
         AND Location = @Location
         AND PropertyID != @propertyID)
FROM Properties
WHERE DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
      AND Location = @Location
      AND PropertyID != @propertyID
End
ElSE
SELECT * ,(SELECT AVG(PRICE) as AveragePrice
      FROM PROPERTIES
          WHERE DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
          AND City = @City
          AND PropertyID != @propertyID)
FROM Properties
WHERE DATEDIFF(day,listingtime,GETDATE()) < @numberOFDays
      AND City = @City
      AND PropertyID != @propertyID
End