Chapter3: DB 2

entity

A CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of ____ integrity.

data dictionary

A ____ contains at least all of the attribute names and characteristics for each table in the system.

secondary

A ____ key is defined as a key that is used strictly for data retrieval purposes.

natural

A(n) ____ join links tables by selecting only the rows with common values in their common attribute(s).

a candidate key can be described as a superkey without unnecessary attributes -- that is, a minimal superkey.

Briefly describe a candidate key:

It provides a detailed description of all tables in the database created by the user and the designer. It contains at least all of the attribute names and characteristics for each table in the system. It contains metadata.

Briefly explain why a data dictionary is necessary, and what should be included in a data dictionary."

synonym

In a database context, a(n) ____ indicates the use of different names to describe the same attribute.

null

In an outer join, the matched pairs would be retained and any unmatched values in the other table would be left ____.

primary

Since it is used to link the tables that originally were related in a M:N relationship, the composite entity structure includes—as foreign keys—at least the ____ keys of the tables that are to be linked.

system catalog

The ____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents. (BTW, in MySQL that database is named "information_schema.")

unique

When you define a table's primary key, the DBMS automatically creates a(n) ____ index on the primary key column(s) you declared.

Referential integrity means that, if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation. Entity integrity ensures that each row is uniquely identified by the primary key.

Why are entity integrity and referential integrity important in a database?

UNION

____ combines all rows from two tables, excluding duplicate rows.

1:M

____ relational type is the "relational model ideal."

INTERESCT

____ yields only the rows that appear in both tables.