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.