Basic Queries¶

This guide covers the fundamentals of querying RDF data with SPARQL.

SELECT Clause¶

The SELECT clause specifies which variables to return:

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

# Select all variables
SELECT *
WHERE { ?s ?p ?o }

# Select specific variables
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?age
WHERE { ?person foaf:name ?name . ?person foaf:age ?age }

# Select with DISTINCT
SELECT DISTINCT ?type
WHERE { ?x rdf:type ?type }

WHERE Clause¶

The WHERE clause contains triple patterns to match:

# Match all triples
SELECT ?s ?p ?o
WHERE { ?s ?p ?o }

# Match triples with a specific predicate
SELECT ?person ?name
WHERE { ?person <http://xmlns.com/foaf/0.1/name> ?name }

# Match triples with a specific object
SELECT ?person
WHERE { ?person rdf:type <http://xmlns.com/foaf/0.1/Person> }

Prefixes¶

Use PREFIX to abbreviate IRIs:

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?name
WHERE {
    ?person rdf:type foaf:Person .
    ?person foaf:name ?name
}

Five prefixes are predefined and work without a PREFIX line: rdf, rdfs, xsd, owl and fn (the XPath functions). A query can redefine any of them with its own PREFIX, and any other prefix it uses without declaring it is a syntax error that names the prefix.

Multiple Triple Patterns¶

Chain triple patterns with . (period):

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

SELECT ?name ?email
WHERE {
    ?person foaf:name ?name .
    ?person foaf:mbox ?email .
    ?person foaf:age ?age
}

Ordering Results¶

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

# Order by a variable
SELECT ?name ?age
WHERE {
    ?person foaf:name ?name .
    ?person foaf:age ?age
}
ORDER BY ?age

# Descending order
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?age
WHERE {
    ?person foaf:name ?name .
    ?person foaf:age ?age
}
ORDER BY DESC(?age)

# Multiple sort keys
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?age
WHERE {
    ?person foaf:name ?name .
    ?person foaf:age ?age
}
ORDER BY DESC(?age) ?name

A sort key can also be an expression or a function call, such as ORDER BY STR(?name) or ORDER BY xsd:double(?price).

Limiting Results¶

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

# Return first 10 results
SELECT ?name
WHERE { ?person foaf:name ?name }
LIMIT 10

# Skip and limit (pagination)
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name
WHERE { ?person foaf:name ?name }
ORDER BY ?name
OFFSET 20 LIMIT 10

ASK Queries¶

Check if a pattern exists. The result is one row holding one Boolean, true when the pattern has a solution and false when it has none, in the column boolean (the name the SPARQL 1.1 Query Results JSON Format gives an ASK result):

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

ASK {
    ?person foaf:name "Alix" .
    ?person foaf:knows ?friend
}

CONSTRUCT Queries¶

Build new RDF triples from query results:

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

CONSTRUCT {
    ?person foaf:fullName ?name
}
WHERE {
    ?person foaf:firstName ?first .
    ?person foaf:lastName ?last
    BIND(CONCAT(?first, " ", ?last) AS ?name)
}

DESCRIBE Queries¶

Get information about a resource:

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

DESCRIBE ?person
WHERE {
    ?person foaf:name "Alix"
}

Blank Nodes¶

Match anonymous nodes:

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

SELECT ?name ?street
WHERE {
    ?person foaf:name ?name .
    ?person foaf:address [
        foaf:street ?street
    ]
}

Named Graph Management¶

SPARQL supports operations on named graphs:

# The source graph must exist: give it a triple first
INSERT DATA {
    GRAPH <http://example.org/source> {
        <http://example.org/alix> <http://xmlns.com/foaf/0.1/name> "Alix" .
    }
}

# Copy all triples from one graph to another (replaces destination)
COPY <http://example.org/source> TO <http://example.org/dest>

# Add triples from source to destination (merge, keeps existing)
ADD <http://example.org/source> TO <http://example.org/dest>

# Move all triples (copy + delete source)
MOVE <http://example.org/source> TO <http://example.org/dest>

A COPY, MOVE or ADD whose source graph does not exist fails ("Source graph <...> does not exist"), as SPARQL 1.1 Update specifies. Use SILENT to skip such a statement without an error:

COPY SILENT <http://example.org/missing> TO <http://example.org/dest>

Insert or delete triples in a specific named graph:

INSERT DATA {
    GRAPH <http://example.org/mygraph> {
        <http://example.org/alix> <http://xmlns.com/foaf/0.1/name> "Alix" .
    }
}

Complete Example¶

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

# Find all people and their friends' names
SELECT ?personName ?friendName
WHERE {
    ?person rdf:type foaf:Person .
    ?person foaf:name ?personName .
    ?person foaf:knows ?friend .
    ?friend foaf:name ?friendName
}
ORDER BY ?personName ?friendName
LIMIT 100