問92
頻出度★★★
関係データベースを構築する際にデータの正規化を行う目的として, 適切なものはどれか。
平成31年度 春期 ITパスポート試験 問92
テクノロジ系データベース › データベース設計
This question's explanation and your answers so far.
解説
問 92
Incorrectア
“Giving data redundancy to detect data errors” is the idea behind error-detection and correction codes such as parity bits and check digits, which instead “add” redundancy. Normalization does the opposite—it “removes” redundancy—so the purpose is exactly reversed.
- イ
正解 Normalization is a design method that splits and organizes the tables of a relational database to eliminate redundancy, the state in which the same data is held in more than one place. When redundancy exists, updating one value while forgetting to fix the other copy creates an “inconsistency”; but by using normalization so that one fact is held in only one place, this update anomaly is prevented and data maintenance and management become easier. Therefore “イ”, which says to “eliminate inconsistencies and duplication in the data, making data maintenance and management easier”, is the correct purpose.
Incorrectウ
Unifying the character encoding is about preventing garbled text or enabling data exchange (character-encoding design), a separate matter from normalization, which organizes table structure. Normalization does not deal with character encoding.
Incorrectエ
Improving access efficiency through lossless compression is the purpose of data-compression technology. Normalization is not a method for compressing data but a logical design method for removing redundancy and inconsistency, so it does not apply.
ここがポイント
- The purpose of normalization is to eliminate data duplication (redundancy) and inconsistency (update anomalies), making maintenance and management easier.
- “Adding redundancy to detect errors” (error-detection codes), “unifying character encoding”, and “lossless compression” are all concepts distinct from normalization and are easily confused distractors.
用語