This is a Database related question: Define each of the following key terms: - B

Question

This is a Database related question:

Define each of the following key terms:
- Base table.
- Data definition language.
- Data manipulation language.
- Dynamic view.
- Materialized view.
- Referential integrity constraint.
- Relational DBMS (RDBMS).
- Schema.
- Virtual table.

Contrast the following terms:
- Base table; view.
- Dynamic view; materialized view.
- Catalog; schema.

Describe a relational DBMS (RDBMS), its underlying data model, data storage structures, and manner of establishing data relationships.

Explanation / Answer

Answers to

a. Base table A table in the relational data model containing inserted raw data that is likely to correspond to one physical file in secondary storage. (The base table is also referred to as one of the objects—such as the base tables, views, constraints, and so on.—which have been defined for a particular database by a particular user, who owns the objects in the schema.)

b. Data definition language Those commands used to define a database, including creating, altering, and dropping tables and establishing constraints.

c.   Data manipulation language Those commands used to maintain and query a database, including updating, inserting, modifying, and querying data.

e. Materialized view Copies or replicas of data based on SQL queries, in the same manner that dynamic views are created. However, a materialized view exists as a table and care must be taken to keep it synchronized with its associated base tables.

g. Relational DBMS (RDBMS) A database management system that manages data as a collection of tables in which all data relationships are represented by common values (not links) in related tables.

h. Schema A structure that contains descriptions of objects created by a user, such as base tables, views, constraints, and so on, as part of a database.

i.   Virtual table A table constructed automatically as needed by a DBMS. Virtual tables are not maintained as real data. Sometimes a virtual table is referred to as a dynamic view.

Contrast the following terms:

a. Base table; view A view is a virtual table and is often part of an external database. In contrast to a defined base table (relation), a view is not permanently represented in storage. A view definition is stored, and the contents of the view are calculated each time the view is referenced in a query. A view may join multiple tables or views together and may contain derived (or virtual) columns, while base tables cannot. In comparison to a temporary real table, a view consumes very little storage space. A view is costly (compared to a dynamic, materialized view), however, because its contents must be calculated each time that it is requested.

   Describe a relational DBMS (RDBMS), its underlying data model, data storage structures, and manner of establishing data relationships:

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