How to filter with WOQL

What you'll achieve By the end of this guide, you will know how to filter query results using WOQL.

Prerequisites: TerminusDB running on localhost:6363 with the Star Wars dataset cloned. If you haven't done this yet, follow the Explore a Real Dataset tutorial (Steps 1–2), or run:
curl -u admin:root -X POST http://localhost:6363/api/clone/admin/star-wars \
  -H "Content-Type: application/json" \
  -H "Authorization-Remote: Basic cHVibGljOnB1YmxpYw==" \
  -d '{"remote_url": "https://data.terminusdb.org/public/star-wars", "label": "Star Wars", "comment": "Star Wars dataset"}'

Since WOQL is a datalog, filters are just part of the query. You can express negative information, or constraints on the variables in order to get a restriction down to the things you want.

For instance, we can write the following query in the query panel for the Star Wars demo:

Example: JavaScript

let v = Vars("person","person_name","vehicle","vehicle_name");
limit(10)
.select(v.person_name, v.vehicle_name)
  .and(triple(v.vehicle, "pilot", v.person),
       triple(v.vehicle, "label", v.vehicle_name),
       triple(v.person, "label", v.person_name))

This results in:

Example: JSON

[ {"person_name": {"@type":"xsd:string", "@value":"Chewbacca"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}},
  {"person_name": {"@type":"xsd:string", "@value":"Han Solo"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}},
  {"person_name": {"@type":"xsd:string", "@value":"Lando Calrissian"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}},
  {"person_name": {"@type":"xsd:string", "@value":"Nien Nunb"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}},
  {"person_name": {"@type":"xsd:string", "@value":"Luke Skywalker"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Wedge Antilles"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Jek Tono Porkins"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Biggs Darklighter"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Darth Vader"},
   "vehicle_name": {"@type":"xsd:string", "@value":"TIE Advanced x1"}},
  {"person_name": {"@type":"xsd:string", "@value":"Boba Fett"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Slave 1"}}
]

We can ask for a specific example of a vehicle name by filtering on equality.

For instance:

Example: JavaScript

let v = Vars("person","person_name","vehicle","vehicle_name");
select(v.person_name, v.vehicle_name)
  .and(triple(v.vehicle, "pilot", v.person),
       triple(v.vehicle, "label", v.vehicle_name),
       triple(v.person, "label", v.person_name),
       eq(v.vehicle_name, string("Millennium Falcon")))

Which results in:

Example: JSON

[ {"person_name": {"@type":"xsd:string", "@value":"Chewbacca"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}},
  {"person_name": {"@type":"xsd:string", "@value":"Han Solo"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}},
  {"person_name": {"@type":"xsd:string", "@value":"Lando Calrissian"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}},
  {"person_name": {"@type":"xsd:string", "@value":"Nien Nunb"},
   "vehicle_name": {"@type":"xsd:string", "@value":"Millennium Falcon"}}
]

We can also write:

Example: JavaScript

let v = Vars("person","person_name","vehicle","vehicle_name");
select(v.person_name, v.vehicle_name)
  .and(triple(v.vehicle, "pilot", v.person),
       triple(v.vehicle, "label", v.vehicle_name),
       triple(v.person, "label", v.person_name),
       not(eq(v.vehicle_name, string("Millennium Falcon"))))

In which we get the complement of the above.

Or, we can use the regex operator to get a wider variety, for instance:

Example: JavaScript

let v = Vars("person","person_name","vehicle","vehicle_name","pattern");
select(v.person_name, v.vehicle_name)
  .and(triple(v.vehicle, "pilot", v.person),
       triple(v.vehicle, "label", v.vehicle_name),
       triple(v.person, "label", v.person_name),
       regex(".*wing", v.vehicle_name, [v.pattern]))

In this case, we get all vehicles whose names end in "wing" — the PCRE pattern .*wing matches any string ending with "wing":

Example: JSON

[ {"person_name": {"@type":"xsd:string", "@value":"Luke Skywalker"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Wedge Antilles"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Jek Tono Porkins"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Biggs Darklighter"},
   "vehicle_name": {"@type":"xsd:string", "@value":"X-wing"}},
  {"person_name": {"@type":"xsd:string", "@value":"Arvel Crynyd"},
   "vehicle_name": {"@type":"xsd:string", "@value":"A-wing"}}
]

Was this helpful?