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