IT 340 - Introduction to Database Systems (Chapter 3)

homonym

are similar-sounding words with different meanings, such as boar and bore, or a word with different meanings, such as fair.

flags

are used to indicate the absence of some value.

system catalog

can be described as a detailed system data dictionary that describes all objects within the database, including data about table names, the table's creator and creation date, the number of columns in each table, the data type corresponding to each column, index filenames, index creators, authorized users, and access privileges.

join column(s)

column(s) that join two tables. The join columns generally share similar values.

key

consists of one or more attributes that determine other attributes.

relational algebra

defines the theoretical way of manipulating table contents using relational operators.

composite entity/bridge entity/associative entity

includes at least the primary keys of the tables to be linked as foreign keys.

theta join

is a join where any other operator other than the equality comparison operator (=) is used.

superkey

is a key that can uniquely any row in the table.

composite key

is a key that is composed of more than one attribute.

set theory

is a mathematical science that deals with sets, or groups of things, and is used as the basis for data manipulation in the relational model.

candidate key

is a minimal superkey - that is, a superkey without any unnecessary attributes.

linking table

is a table that links two tables in a many to many relationship.

relvar

is a variable that holds a relation.

primary key (PK)

is an attribute or combination of attributes that uniquely identifies any given row.

key attribute

is an attribute that is a part of a key.

index

is an orderly arrangement used to logically access rows in a table.

secondary key

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

null

is the absence of any data value, and it is never allowed in any part of the primary key.

determinant

is the attribute whose value determines another.

dependent

is the attribute whose value is determined by another attribute.

domain

is the column's range of permissible values.

entity integrity

is the condition in which each row (entity instance) in the table has its own unique identity.

referential integrity

is the condition in which every reference to an entity instance by another entity instance is valid.

index key

is the index's reference point.

synonym

is the opposite of a homonym, and indicates the use of different names to describe the same attribute.

foreign key (FK)

is the primary key of one table that has been placed into another table to create a common attribute.

attribute domain

is the specific range of values for each column.

determination

is the state in which knowing the value of one attribute makes it possible to determine the value of another.

closure

is the use of relational algebra operators on existing relations (tables) produces new relations.

full functional dependence

is used to refer to functional dependencies in which the entire collection of attributes in the determinant is necessary for the relationship.

union-compatible

is whether two tables can have a union between them.

natural join

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

equijoin

links tables on the basis of an equality condition that compares specified columns of each table.

functional dependence

means that the value of one or more attributes determines the value of one or more other attributes.

inner join

only returns matched records from the tables that are being joined.

data dictionary

provides a detailed description of all tables in the database created by the user and designer.

tuple/row

represents a single entity occurrence within the entity set.

unique index

the index key can have only one pointer value (row) associated with it.

outer join

the matched pairs would be retained, and any unmatched values in the other table would be left null.

predicate logic

which is used extensively in mathematics, provides a framework in which assertion (statement of fact) can be verified as true or false.

left outer join

yields all of the rows in the left table, includes those that do not have a matching value in the right table.

right outer join

yields all of the rows in the right table, includes those that do not have a matching value in the left table.