📓 pages/Exploratory queries.md by @sparql ☆

Properties in use

SELECT DISTINCT ?property 
WHERE { ?s ?property ?o . }

Properties ranked by use

SELECT ?p (COUNT (DISTINCT ?o) AS ?nv)

WHERE {
    ?s ?p ?o 
}

GROUP BY ?p
ORDER BY DESC (?nv)

#Query #COUNT #[[GROUP BY]]

Classes

SELECT DISTINCT ?class 
WHERE { ?s a ?class . }

All triples
- Asking for all triples makes sense when you know that the dataset is small.
- Most triple stores will give all accessible data with SELECT * {?s ?p ?o} but some my give only the triples in the default graph so it’s better to ask explicitly for all the triples in all named graphs.
  - ```
  SELECT ?g ?s ?p ?o
  WHERE
  {
  	{ ?s ?p ?o }
  	UNION
  	{ GRAPH ?g { ?s ?p ?o } }
  }
```#Query #GRAPH #UNION
```
- Total number of triples (from all graphs)
  - ```
  SELECT (COUNT (?s) as ?Number_of_triples)
  
  {
     { ?s ?p ?o } UNION { GRAPH ?g { ?s ?p ?o } }
  }
```
  #Query #COUNT #GRAPH #UNION
- Total number of triples (from all graphs) per graph
  - ```
  SELECT ?g (COUNT (?s) as ?Number_of_triples)
  
  
  {
     { ?s ?p ?o } UNION { GRAPH ?g { ?s ?p ?o } }
  }
  
  ORDER BY DESC (?Number_of_triples)
```
  #Query #COUNT #GRAPH #UNION

Sample entity and count

SELECT (SAMPLE(?s) as ?sample) (count(?s) as ?count) ?class

WHERE {?s a ?class }

GROUP BY ?class
ORDER BY DESC(?count)