Friday, March 25, 2016

Data Fundamentals for Analysts: Not Worth Repeating - Duplicates

“Stating the same fact more than once, does not make it truer, only redundant,” as E. F. Codd used to say. 

Frequent hits @dbdebunk.com are driven by the question “Are keys mandatory?” Puzzlingly, many data professionals do not seem to understand why duplicates should be prohibited. This should worry analysts.
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But the absence of an identifier means that individual entities are not meaningful, so this representation contradicts the real world. Contradictions produce problems. First, a DBMS is incapable of “visually” discerning a data entry duplication error from "valid" duplicates, which means high risk of inconsistent databases and wrong counts and other query results.

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