SQL can do recursive rules too. SQL tutorials often do SQL a disservice by introducing it as a database query language rather than relational algebra :) exam

SQL can do recursive rules too. SQL tutorials often do SQL a disservice by introducing it as a database query language rather than relational algebra :) example=# select * from move; place | method | newplace ---------+--------+---------- home | taxi | halifax halifax | train | gatwick gatwick | plane | rome (3 rows) example=# create view on_route as with recursive on_route(place, newplace, length, path) as (select place, newplace, 1 as length, place as path FROM move UNION select on_route.place, move.newplace, on_route.length + 1, path || '->' || move.place as path FROM move JOIN on_route ON on_route.newplace = move.place) SELECT place, newplace, length, path || '->' || newplace as path FROM on_route; CREATE VIEW example=# select distinct true from on_route WHERE place = 'home' and newplace = 'rome'; bool ------ t (1 row) example=# select path from on_route WHERE place = 'home' and newplace = 'rome'; path ------------------------------ home->halifax->gatwick->rome