Containment of Conjunctive Queries over Databases with Null Values
نویسندگان
چکیده
We study containment of conjunctive queries that are evaluated over databases that may contain tuples with null values. We assume the semantics of SQL for single block queries with a SELECT DISTINCT clause. This problem (“null containment” for short) is different from containment over databases without null values and sometimes more dif-
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