問63
頻出度★★★
関係データベースを利用する際に, 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21年度 秋期 ITパスポート試験 問63
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 63
Incorrectア
Data compatibility between computers of different types is ensured by standardizing character codes and data formats (adopting a common file format and character code system). Normalization is a design method for organizing the table structure inside a single database, and has nothing to do with compatibility across machine types.
- イ
正解 Normalization is a method used when designing the tables of a relational database: repeating items and items that depend on other items are split out, the table is divided into several tables, and the same data is no longer held in duplicate in multiple places. If a piece of data exists in only one place, an inconsistency such as updating one copy while another copy stays out of date (an update anomaly) cannot occur in principle. The purpose of normalization is therefore to “prevent data from being duplicated and prevent inconsistencies from arising when updating data”, so イ is correct.
Incorrectウ
Removing characters that cannot be handled in transmission, or converting them into another representation, is the job of encoding processing during communication (character code conversion and escape processing). The term normalization does not refer to character handling in the communications field.
Incorrectエ
Making storage areas spanning multiple media appear as one contiguous area is a function of the OS virtual memory or volume management (logical volumes). Normalization is not about how physical storage areas are presented, but about the logical structure of tables.
ここがポイント
- Normalization = a database design method that splits tables to eliminate duplication and prevent update anomalies (inconsistencies on update, insert, and delete). Its purpose is to ensure consistency, not to improve performance or optimize physical placement.
- Distinguish it from confusable terms in other fields: compatibility across machine types comes from standardizing data formats and character codes, character handling for transmission is encoding, and the mechanism that makes storage look contiguous is virtual memory / volume management.
用語