Data Model: A set of concepts to describe the structure of a database, and certain constraints that the database should obey.
Data Model Operations: Operations for specifying database retrievals and updates by referring to the concepts of the data model. Operations on the data model may include basic operations and user-defined operations.
A crucial property of a relational DBMS is that it provides
physical data independence. This allows physical structures such
as indexes to change seamlessly without affecting the output of
the query; but such changes do impact efficiency. Thus, together
with the capabilities of the execution engine and the optimizer,
the physical database design determines how efficiently a query is
executed on a DBMS.
The first generation of relational execution engines were
relatively simple, targeted at OLTP, making index selection less
of a problem.
The minimum number of Cs that can be associated with one A is 1. I know this because the existence of the C to A relationship is mandatory. The maximum number of Cs that can be associated with one A is unlimited (or many). I know this because the cardinality of the C to A relationship is 1-M.
Câu 1: A problem soling technique that decomposes a system its component parts while
focusing on the business problem independent of technology is:
a. Cause-and-effect analysis.
b. System design.
c. Joint application design(JAD).
d. Systems analysis.
Câu 2: A database is an organized collection of ____ related data.
a. None of the others answers.