問65
頻出度★★★
DBMS において, データの検索を高速に行う目的で, 必要に応じて設定して利用する情報はどれか。
令和7年度 ITパスポート試験 問65
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 65
- ア
正解 The correct answer is ア (Index). An index is auxiliary information that maps the values of a specific column in a table to their storage locations, allowing the system to reach the target data quickly without scanning every record in order. The statement in the question—“set up and used as needed for the purpose of searching data at high speed”—accurately describes the characteristics of an index. An index is optional information that the designer can freely create or delete as needed for search performance, so it is the correct answer.
Incorrectイ
A foreign key is a constraint that maps a column of one table to the primary key of another table, ensuring referential integrity (relationships) between tables. Its purpose is to relate data and maintain integrity, not to be set up for speeding up searches, so it is incorrect.
Incorrectウ
A primary key is a column (or combination of columns) used to uniquely identify each row in a table, allowing neither duplicates nor null values. Its purpose is to guarantee the uniqueness of rows, not to be “set up arbitrarily as needed” for speeding up searches (it is an almost mandatory constraint in table design), so it is incorrect.
Incorrectエ
A schema is the definition of the overall structure of a database (tables, columns, data types, constraints, relationships, etc.), corresponding to the blueprint of the database. It is definitional information, not information set up for the purpose of speeding up searches, so it is incorrect.
ここがポイント
- Index = auxiliary information set up arbitrarily on a column to speed up searches. The idea is the same as the index used when looking something up in a book: it avoids a full scan and reaches the target row quickly.
- Distinguishing the main kinds of information in a DBMS: primary key (uniquely identifies a row) / foreign key (referential integrity between tables) / schema (structural definition of the whole database) / index (speeds up searches)—identify them by the difference in purpose.
用語