問54
頻出度★★★
関係データベースの設計に関する説明において，a～cに入れる字句の適切な組合せはどれか。 対象とする業務を分析して，そこで使われるデータを洗い出し，実体や[ a ]から成る[ b ]を作成する。作成した[ b ]をもとに，[ c ]を設計する。
平成27年度 秋期 ITパスポート試験 問54
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 54
Incorrectア
The “E-R diagram” in b is correct, but “instance” in a is wrong. An instance refers to the concept of the specific individual pieces of data (actual values) of an entity, whereas the elements that make up an E-R diagram are entities and “relationships”. Also, the “function” in c is a processing unit of a program, not something designed based on an E-R diagram.
Incorrectイ
The “instance” in a is wrong (the correct term is relationship). Furthermore, the “flowchart” in b represents the steps and flow of processing; it is not a diagram of a data structure made up of entities and relationships. The “table” in c is correct, but because a and b are wrong, this combination is inappropriate.
- ウ
正解 Relational database design begins with the step of identifying and diagramming “entities” and “the connections between entities, i.e. relationships”. Therefore blank a is “relationship”. The diagram that represents entities and relationships is the “E-R diagram (Entity-Relationship diagram)”, so b is “E-R diagram”. Then, based on the data structure organized in the E-R diagram, you design the “table”, which is the implementation unit of a relational database, so c is “table”. Thus the combination a=relationship / b=E-R diagram / c=table, namely option ウ, is correct.
Incorrectエ
The “relationship” in a is correct, but the “flowchart” in b is wrong. What is created from entities and relationships is an E-R diagram, not a flowchart. Also, the “function” in c is wrong; what is designed based on an E-R diagram is the table.
ここがポイント
- The flow of relational database design: identify the data through business analysis, create an E-R diagram from entities and relationships, and then design the table based on it.
- An E-R diagram is a data model that diagrams entities and relationships; distinguish it from a flowchart, which represents the flow of processing, as the two serve different purposes.
用語