Abstract:
In the frame of the previous research it is asummed that relations tuples are identically distributed and the values of different attributes are independent.
These assumptions are not realistic because attributes values can be imprecise and there can be a dependency between attributes.
In this paper we extend the concept of selectivity factor, associated to a query to the notion of selectivity factor associated to queries sets and we give some practical results in the case of random databases.
Key Words: Database, selectivity factor, relational operators, cardinality.
2000 Mathematics Subject Classification: Primary: 68P15;
Secondary: 68P20, 68P10.
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