I have a table that has customer_number, customer_location(lat, long), current_latched_tower_ID, tower_location(lat,long) and Distance(between cx location and latched tower location). I am trying to find a tower that is very closer to the customer location rather than current_latched_tower.

Example: One customer currently latched to one tower(KA001), the distance between customer location and latched tower location is 1.6KM. However, there is another tower(KA002) very closer to the customer location. Thus, its distance between customer location and closest tower location is 1.3KM.

Table

customer_number   cx_lat       cx_long      tower_lat   tower_long  Latched_tower_ID   Distance
34532             6.897257333  79.86474533  6.890487    79.869199   CM0321             0.51477
43445             6.935598403  81.14939421  6.947618    81.160246   BD0010             1.2292
54365             6.866224     79.88215     6.896111    79.868611   CM0037             1.6216
52568             7.113198     80.037247    7.121666    80.028888   GM0121             0.9476

Expecting output table

customer_number   cx_lat       cx_long      tower_lat   tower_long  Latched_tower_ID   Distance  Cloesed_tower_ID  Closed_Distance
34532             6.897257333  79.86474533  6.890487    79.869199   CM0321             0.51477   CM0037            0.43222
52568             7.113198     80.037247    7.121666    80.028888   GM0121             0.9476  NULL                NULL

if don't have any closer tower rather than latched tower "Cloesed_tower_ID" and "Closed_Distance" columns should be NULL

CodePudding user response：

If you are not using SDO_GEOM then you can create the haversine function to calculate the distance between two latitude/longditude co-ordinates:

CREATE FUNCTION haversine_distance(
  lat1  IN NUMBER,
  long1 IN NUMBER,
  lat2  IN NUMBER,
  long2 IN NUMBER
) RETURN NUMBER DETERMINISTIC
IS
  PI           CONSTANT NUMBER := ASIN(1) * 2;
  R            CONSTANT NUMBER := 6371000; -- Approx. radius of the earth in m
  PHI1         CONSTANT NUMBER := lat1 * PI / 180;
  PHI2         CONSTANT NUMBER := lat2 * PI / 180;
  DELTA_PHI    CONSTANT NUMBER := (lat2 - lat1) * PI / 180;
  DELTA_LAMBDA CONSTANT NUMBER := (long2 - long1) * PI / 180;
  a NUMBER;
  c NUMBER;
BEGIN
  a := SIN(delta_phi/2) * SIN(delta_phi/2)   COS(phi1) * COS(phi2) *
          SIN(delta_lambda/2) * SIN(delta_lambda/2);
  c := 2 * ATAN2(SQRT(a), SQRT(1-a));
  RETURN R * c; -- in metres
END;
/

Then, I am assuming that you have your data in third normal form:

CREATE TABLE towers (
  tower_id PRIMARY KEY,
  t_lat,
  t_long
) AS
SELECT 'CM0321', 6.890487, 79.869199 FROM DUAL UNION ALL
SELECT 'BD0010', 6.947618, 81.160246 FROM DUAL UNION ALL
SELECT 'CM0037', 6.896111, 79.868611 FROM DUAL UNION ALL
SELECT 'GM0121', 7.121666, 80.028888 FROM DUAL;

CREATE TABLE customers (
  customer_number PRIMARY KEY,
  cx_lat,
  cx_long,
  latched_tower_id
) AS
SELECT 34532, 6.897257333, 79.86474533, 'CM0321' FROM DUAL UNION ALL
SELECT 43445, 6.935598403, 81.14939421, 'BD0010' FROM DUAL UNION ALL
SELECT 54365, 6.866224000, 79.88215000, 'CM0037' FROM DUAL UNION ALL
SELECT 52568, 7.113198000, 80.03724700, 'GM0121' FROM DUAL;

ALTER TABLE customers ADD CONSTRAINT customers__lti__fk
  FOREIGN KEY (latched_tower_id) REFERENCES towers (tower_id);

Then, from Oracle 12, you can calculate the closer towers using:

SELECT c.*,
       TO_CHAR(
         HAVERSINE_DISTANCE(c.cx_lat, c.cx_long, t.t_lat, t.t_long)/1000,
         'FM999990.000'
       ) AS distance,
       ct.tower_id AS closer_tower_id,
       TO_CHAR(ct.distance, 'FM999990.000') AS closer_distance
FROM   customers c
       INNER JOIN towers t
       ON (t.tower_id = c.latched_tower_id)
       LEFT OUTER JOIN LATERAL(
         SELECT ct.*,
                HAVERSINE_DISTANCE(
                    c.cx_lat,
                    c.cx_long,
                    ct.t_lat,
                    ct.t_long
                )/1000 AS distance
         FROM   towers ct
         ORDER BY distance ASC
         FETCH FIRST ROW ONLY
       ) ct
       ON (ct.tower_id != c.latched_tower_id);

Which outputs:

CUSTOMER_NUMBER	CX_LAT	CX_LONG	LATCHED_TOWER_ID	DISTANCE	CLOSER_TOWER_ID	CLOSER_DISTANCE
43445	6.935598403	81.14939421	BD0010	1.795
54365	6.866224	79.88215	CM0037	3.644	CM0321	3.053
34532	6.897257333	79.86474533	CM0321	0.899	CM0037	0.445
52568	7.113198	80.037247	GM0121	1.318

Before Oracle 12, you can use:

SELECT customer_number,
       cx_lat,
       cx_long,
       latched_tower_id,
       distance,
       CASE
       WHEN latched_tower_id != closer_tower_id
       THEN closer_tower_id
       END AS closer_tower_id,
       CASE
       WHEN latched_tower_id != closer_tower_id
       THEN closer_distance
       END AS closer_distance
FROM   (
  SELECT c.*,
         TO_CHAR(
           HAVERSINE_DISTANCE(c.cx_lat, c.cx_long, t.t_lat, t.t_long)/1000,
           'FM999990.000'
         ) AS distance,
         ct.tower_id AS closer_tower_id,
         TO_CHAR(
           HAVERSINE_DISTANCE(c.cx_lat, c.cx_long, ct.t_lat, ct.t_long)/1000,
           'FM999990.000'
         ) AS closer_distance,
         ROW_NUMBER() OVER (
           PARTITION BY c.customer_number
           ORDER BY HAVERSINE_DISTANCE(c.cx_lat, c.cx_long, ct.t_lat, ct.t_long)
         ) AS rn
  FROM   customers c
         INNER JOIN towers t
         ON (t.tower_id = c.latched_tower_id)
         CROSS JOIN towers ct
  ORDER BY
         customer_number,
         DISTANCE ASC
)
WHERE  rn = 1;

db<>fiddle here