1. SPARQL
RDF Query

2. Query RDF: SPARQL
The Simple Protocol and RDF Query Language (SPARQL) is a SQL-like language for querying RDF data. For expressing RDF graphs in the matching part of the query, TURTLE syntax is used.

3. A Query Template
I want these pieces of information from the subset of the data that meets these conditions.
You describe the conditions with triple patterns, which are similar to RDF triples but may include variables to add flexibility in how they match against the data.

4. Craig has two email addresses:

7. The query to find Craig’s email addresses would then look like this:

8. A SELECT query PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?mbox
WHERE { ?x foaf:name ?name .
?x foaf:mbox ?mbox . }
first line defines namespace prefix
the last two lines use the prefix to express a RDF graph to be matched
Identifiers beginning with question mark ? identify variables
In this query, we are looking for resource ?x participating in triples with predicates foaf:name and foaf:mbox and want the objects of these triples

9. PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?url
FROM <bloggers.rdf>
WHERE {
?contributor foaf:name "Jon Foobar" .
?contributor foaf:weblog ?url . }

10. Data
< < "SPARQL Tutorial" .
Query
SELECT ?title
WHERE {
< < ?title . }
Result
“SPARQL Tutorial"

11. The result of a query is a solution sequence, corresponding to the ways in which the query's graph pattern matches the data. There may be zero, one or multiple solutions to a query.

12. Data:
@prefix foaf: < .
_:a foaf:name "Johnny Lee Outlaw" .
_:a foaf:mbox .
_:b foaf:name "Peter Goodguy" .
_:b foaf:mbox .
_:c foaf:mbox .
Query:
PREFIX foaf: <
SELECT ?name ?mbox
WHERE
{ ?x foaf:name ?name .
?x foaf:mbox ?mbox }
Query Result:
name mbox
"Johnny Lee Outlaw"
"Peter Goodguy"

13. SELECT ?x
WHERE { ?x < "John Smith" }
SELECT ?x ?fname
WHERE {?x < ?fname}
SELECT ?givenName
WHERE
{ ?y < "Smith" .
?y < ?givenName . }
PREFIX vcard: <
SELECT ?givenName
WHERE
{ ?y vcard:Family "Smith" .
?y vcard:Given ?givenName . }

14. SPARQL Tutorial - Filters
SPARQL provides an operation to test strings, based on regular expressions. 
Syntax is
FILTER regex(?x, "pattern" [, "flags"])
PREFIX vcard: <
SELECT ?g
WHERE
{ ?y vcard:Given ?g .
FILTER regex(?g, "r", "i") }
Result:
"Rebecca"
"Sarah"
The flag "i" means a case-insensitive pattern match is done

15. PREFIX info: <http://somewhere/peopleInfo#>
SELECT ?resource
WHERE {
?resource info:age ?age .
FILTER (?age >= 24) }
PREFIX info: <
PREFIX vcard: <
SELECT ?name ?age
WHERE {
?person vcard:FN ?name .
OPTIONAL { ?person info:age ?age } }
gets the name of a person and also their age if that piece of information is available.

16. PREFIX info: <http://somewhere/peopleInfo#>
PREFIX vcard: <
SELECT ?name ?age
WHERE {
?person vcard:FN ?name .
OPTIONAL { ?person info:age ?age . FILTER ( ?age > 24 ) } }

17. A query to find people described in two named FOAF graphs
PREFIX foaf: <
PREFIX rdf: <
SELECT ?name
FROM NAMED <jon-foaf.rdf>
FROM NAMED <liz-foaf.rdf>
WHERE {
GRAPH <jon-foaf.rdf> {
?x rdf:type foaf:Person .
?x foaf:name ?name .
} .
GRAPH <liz-foaf.rdf> {
?y rdf:type foaf:Person .
?y foaf:name ?name . }