| # An optional and an fixed pattern | |
| PREFIX : <http://example.org/> | |
| # Ensure an optional does not mask a later one. | |
| # This query works unreordered because it has written out the needed UNION | |
| SELECT * | |
| WHERE | |
| { | |
| :x :p ?v . | |
| OPTIONAL {:y ?p ?a } | |
| OPTIONAL {:z ?p ?v } | |
| } | |
| ## SELECT DISTINCT * | |
| ## { | |
| ## :x :p ?v . | |
| ## { OPTIONAL {:y ?p ?a } OPTIONAL {:z ?p ?v } } | |
| ## UNION | |
| ## { OPTIONAL {:z ?p ?v } OPTIONAL {:y ?p ?a } } | |
| ## } | |