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Query Variable

A query variable is a proxy for the object(s) you are searching for when constructing a SPARQL query. SPARQL queries are composed of triples: a subject, predicate, and object. In SPARQL queries, each component of the triple needs to be either a query variable or a Uniform Resource Identifier (URI).

Query variables are indicated with a question mark or dollar sign followed by a word. The word you choose for a variable is arbitrary, but should be human-readable for ease of understanding, and must be used consistently within a query.

Examples​

  • Lincoln (2015) “Using SPARQL to Access Linked Open Data”: In the following query, the variable is ?painting. This variable tells the triplestore to search for all values of ?painting that properly complete the statement <has medium><oil on canvas>. ?painting stands in for the node(s) that the database will return.

    SELECT ?painting
    WHERE {
       ?painting <has medium> <oil on canvas> .
     }