問86
頻出度★★★
DBMS におけるインデックスに関する記述として, 適切なものはどれか。
平成30年度 春期 ITパスポート試験 問86
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 86
- ア
正解 The correct answer is ア. An index is auxiliary data (information) that is set up and used as needed on the columns of a table for the purpose of speeding up searches. Like the index at the back of a book, it is a mechanism for quickly locating where a target record is; searches can still be performed without it, but with it you can find records quickly while avoiding a full scan of every record. Choice ア exactly matches the description of information that is set up and used as needed for the purpose of performing searches quickly, so it is correct.
Incorrectイ
The description of an indivisible unit of processing that combines multiple mutually related or dependent processes into one refers to a transaction, not an index. A transaction is a group of operations that guarantees either all succeed or all are canceled (atomicity).
Incorrectウ
The description of a referential integrity constraint between two tables refers to a referential integrity constraint enforced by a foreign key, not an index. It is a mechanism that prevents data inconsistency by guaranteeing that a value in one table exists in another table.
Incorrectエ
The description of a field used to uniquely identify a record refers to a primary key, not an index. A primary key is a column used to distinguish each row of a table without duplication; its purpose is unique identification, not speeding up searches.
ここがポイント
- An index is auxiliary information set up on a table as needed in order to speed up searches; searches can be done without it, but adding one makes them faster.
- Distinguishing easily confused database terms: an index differs in role from a transaction (an indivisible unit of processing), a primary key (unique identification of a record), and a foreign key / referential integrity constraint (consistency between two tables).
用語