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Why Are Functional Dependencies Not Equations? |
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Answer» Equations deal with numerical relationships. A functional DEPENDENCY deals with the existence of a DETERMINANT relationship between ATTRIBUTES, regardless of whether or not there is a numerical relationship between them. Thus, if we know that there is no hot WATER every Wednesday, No-Hot-Water is functionally DEPENDENT on Wednesday. So, if we know it is Wednesday, then we know we will have No-Hot-Water. This is a functional dependency, but not an equation. Equations deal with numerical relationships. A functional dependency deals with the existence of a determinant relationship between attributes, regardless of whether or not there is a numerical relationship between them. Thus, if we know that there is no hot water every Wednesday, No-Hot-Water is functionally dependent on Wednesday. So, if we know it is Wednesday, then we know we will have No-Hot-Water. This is a functional dependency, but not an equation. |
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