How to get shortest path between source and destination - mysql

Question

My Mysql table consist as follows
I want to get shortest path from here. I tried 'WITH RECURSIVE' way. but it gives mysql error. Is there any way of doing that? I want to list items which gives shortest path.

Answer 1

You can do something like this, but note that this scales abysmally poorly for larger data sets...
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(id SERIAL PRIMARY KEY
,origin VARCHAR(12) NOT NULL
,destination VARCHAR(12) NOT NULL
,distance INT NOT NULL
,UNIQUE(origin,destination)
);
INSERT INTO my_table VALUES
(1,'MILAN','TURIN',150),
(2,'TURIN','MILAN',150),
(3,'MILAN','VENICE',250),
(4,'VENICE','MILAN',250),
(5,'MILAN','GENOA',200),
(6,'MILAN','ROME',600),
(7,'ROME','MILAN',600),
(8,'MILAN','FLORENCE',380),
(9,'TURIN','GENOA',160),
(10,'GENOA','TURIN',160),
(11,'FLORENCE','VENICE',550),
(12,'FLORENCE','ROME',220),
(13,'ROME','FLORENCE',220);
SELECT x.origin
, y.origin waypoint1
, z.origin waypoint2
, COALESCE(z.destination,y.destination,x.destination) destination
, x.distance+COALESCE(y.distance,0)+COALESCE(z.distance,0) distance
FROM my_table x
LEFT
JOIN my_table y
ON y.origin = x.destination
AND y.destination <> x.origin
LEFT
JOIN my_table z
ON z.origin = y.destination
AND z.destination <> y.origin
AND z.destination <> x.origin
WHERE x.origin = 'ROME'
HAVING destination = 'VENICE'
ORDER
BY distance LIMIT 1;
+--------+-----------+-----------+-------------+----------+
| origin | waypoint1 | waypoint2 | destination | distance |
+--------+-----------+-----------+-------------+----------+
| ROME | MILAN | NULL | VENICE | 850 |
+--------+-----------+-----------+-------------+----------+