Pretest 1 PDBMS

Which statement is not correct?

• The file-based approach to data management causes the same information to be stored separately for different applications.

• In a file-based approach to data management, the data definitions are included in each application separately.

• In a file-based approach to data management, different applications could be using older and newer versions of the same data.

• In a file-based approach to data management, a change in the structure of a data file is easily handled because each application has its own data files.

Which statement is not correct?

• In a database approach, applications don’t have their own files, but all applications access the same version of the data by interfacing with the DBMS.

• In a database approach, the data definitions or metadata are stored in the applications accessing the data.

• In a database approach, there is typically less storage needed compared to the file approach.

• In a database approach, maintenance of data and metadata is easier.

Which statement is not correct?

• In a file-based approach, every application has its own query and access procedures, even if they want to access the same data.

• SQL is a database language to manage DBMSs without having to write a substantial amount of programming code.

• SQL is a database language that focuses on how to access and retrieve the data.

• SQL is a database language that allows different applications to access different subsets of the data necessary for each application.

Which statement is not correct?

• In a conceptual data model, the data requirements from the business should be captured and modeled.

• A conceptual data model is implementation-dependent.

• A logical data model translates the conceptual data model to a specific implementation environment.

• Examples of implementations of logical data models are hierarchical, CODASYL, relational, or object-oriented models.

Complete the following sentence, choosing the right words in positions A and B. A(n) …A… data model is the mapping of a(n) …B… data model to a model that describes which data are stored where and in what format.

• A: internal, B: logical.

• A: conceptual, B: internal.

• A: logical, B: internal.

• A: logical, B: conceptual.

What concept specifies the various data items, their characteristics, and relationships, constraints, storage details, etc. and is specified during the database design?

• Database model.

• Catalog

• Database state

• None of the above

Which statement regarding the database state is correct?

• The database state represents the data in the database when the database is first created

• The database state changes when data are updated or removed

• The database state specifies the various data items, their characteristics, and relationships, and is specified during the database design

• The database state is stored in the catalog

Complete this sentence: In the three-layer architecture, between the external layer and the conceptual/logical layer, there is …

• physical data independence

• logical data independence

• no independence, they are basically the same thing

• the internal layer

Which statement is correct?

Statement A: The middle layer of the three-layer architecture consists of both the conceptual data model and the logical data model. The logical data model is physically implemented in the internal layer.

Statement B: The top level of the three-layer architecture is the external layer. Views for one or more applications always offer a window on the complete logical model.

• Only sentence A is right

• Only sentence B is right

• Sentences A and B are right

• Neither A nor B is right

Which statement is correct?

Statement A: DDL is the language used to define the logical data model, but no other data models.

Statement B: SQL is a DML language to retrieve, insert, delete, and modify data. It is stored in the catalog.

• Only A

• Only B

• A and B

• Neither A nor B