Making function for calculating distance

I wish did fix the issue. Your distance function should not necessarily be anywhere near your two original curves: It's using a completely different coordinate system, i.e. t vs D, as opposed to your original curves using x and y. [edit] i.e. t only goes up to 1.0, and measures how far along, as a ratio of the total length, you are along your curve, and D measuring the distance your curve2 is from curve1's baseline.
Also, when you say ""distance function" between curve1 and a "baseline" of curve2" I think you've mixed up curve1 and curve2 here as in your code you are clearly using the baseline of curve1.

seems to work fine all. , Okay.
Solved it.

 DELIMITER $$
 CREATE FUNCTION haversineDistance
                 (
                  lat1 VARCHAR(256), 
                  long1 VARCHAR(256), 
                  lat2 VARCHAR(256), 
                  long2 VARCHAR(256))
 RETURNS FLOAT DETERMINISTIC
 BEGIN

      DECLARE radLat1 FLOAT;
      DECLARE radLong1 FLOAT;
      DECLARE radLat2 FLOAT;
      DECLARE radLong2 FLOAT;
      DECLARE dLat FLOAT;
      DECLARE dLong FLOAT;
      DECLARE cordLength FLOAT;
      DECLARE centralAngle FLOAT;
      DECLARE distance FLOAT;

      SET radLat1 = CAST(lat1 AS DECIMAL(10,10)) * PI() / 180;
      SET radLong1 = CAST(long1 AS DECIMAL(10,10)) * PI() / 180;
      SET radLat2 = CAST(lat2 AS DECIMAL(10,10)) * PI() / 180;
      SET radLong2 = CAST(long2 AS DECIMAL(10,10)) * PI() / 180;
      SET dLat = radLat2 - radLat1;
      SET dLong = radLong2 - radLong2;
      SET cordLength = POW(SIN(dLat/2),2)+COS(lat1)*COS(lat2)*POW(SIN(dLon/2),2);
      SET centralAngle = 2 * ATAN2(SQRT(cordLength), SQRT(1-cordLength));
      SET distance = 6367 * centralAngle;

      RETURN distance;
 END

Hope this helps I have a table of which first 3 rows look like: , Please Modify your query as below:

        SELECT IDENTITY(INT, 1, 1) ID
            ,*
            ,CAST(0 AS FLOAT) dist1
            ,CAST(0 AS FLOAT) DIST2
        INTO #TEMP
        FROM #zip

        DECLARE @COUNT INT
        ,@DIST1 FLOAT
        ,@DIST2 FLOAT
        ,@MAXID INT

        SET @COUNT = 1

        SELECT @MAXID = MAX(ID)
        FROM #TEMP

        WHILE (@COUNT <= @MAXID)
        BEGIN
            SELECT @DIST1 = dbo.ufnzipcodedist_2012(z1, z2)
                ,@DIST2 = dbo.ufnzipcodedist_2012(z2, z3)
            FROM #TEMP
            WHERE ID = @COUNT

            UPDATE t
            SET T.DIST1 = @DIST1
                ,t.DIST2 = @DIST2
            FROM #TEMP t
            WHERE ID = @COUNT

            SET @COUNT = @COUNT + 1
        END

        SELECT *
        FROM #TEMP

it helps some times It could be that the zip code on its own is ambiguous. If you include 'USA' in the search string it works

library(ggmap)

mapdist(from = c("19111, USA"), to = c("19187, USA"))


#         from         to     m    km    miles seconds  minutes     hours
# 1 19111, USA 19187, USA 21420 21.42 13.31039    1976 32.93333 0.5488889

library(googleway)

set_key("your_api_key")

google_distance(origins = c("19111, USA"), 
                destinations = c("19187, USA"))

# $destination_addresses
# [1] "Philadelphia, PA 19187, USA"
# 
# $origin_addresses
# [1] "Philadelphia, PA 19111, USA"
# 
# $rows
# elements
# 1 21.4 km, 21420, 33 mins, 1976, 35 mins, 2101, OK
# 
# $status
# [1] "OK"