Chapter 9
hashed file organization
address for each row is determined using an algorithm
foreign key
attribute that appears as a non primary key attribute in one relation and as a primary key attribute in another relation
primary key
attribute whose value is unique across all occurrences of a relation
data type
coding scheme recognized by system software for representing organizational data
view integration
combine normalized data requirements from all user interfaces into one consolidated logical database model
referential integrity
integrity constraint specifying that the value of an attribute in one relation depends on the value of the same attribute in another relation
physical table
named set of rows and columns that specifies the fields in each row of the table
physical file
names set of table rows stored in a contiguous section of secondary memory
secondary key
one or a combination of fields for which more than one row may have the same combinations of values
functional dependency
particular relationship between two attributes
input mask
pattern of codes that restricts the width and possible values for each position of a field
determinants
primary keys of the relations used to create new relations
normalization
process of converting complex data strikers into simple, stable data structures
denormalization
process of splitting or combining normalized relations into physical tables based on affinity of use of rows and fields
second normal form
relation for which every non primary key attribute is functionally dependent on the whole primary key
well-structured relation
relation that contains a minimum amount of redundancy and allows users to insert, modify, and delete the rows without errors or incompleteness
third normal form
relation that is in second normal form and has no functional (transitive) dependencies between two (or more) non primary key attributes
recursive relationships
relationship between the instances of a single entity type
indexed file organization
rows are stored either sequentially or consequentially, and an index is created that allows software to locate individual rows
sequential file organization
rows in the file are stored in sequence according to a primary key value
homonym
single attribute name that is used for two or more different attributes
field
smallest unit of name application data recognized by system software
null value
special field value, distinct from 0, blank, or any other value, that indicates that the value for the field is missing or otherwise unknown
index
table used to determine the location of rows in a file that satisfy some condition
file organization
technique for physically arranging the records of a file
synonyms
two different names that are used for the same attribute
redundant relations
two or more relations that describe the same entity type
default value
value a field will assume unless an explicit value is entered for that field
data structure
grouping attributes from the logical database model into physical records
relational
a named, two-dimensional table of data
range control
both numeric and alphabetic data may have a limited set of permissible values
transitive dependency
functional dependency between non primary key attributes
relational database model
data represented as a set of related tables or relations
normalized relation
description of associated database requirements
weak entity
entity whose primary key depends upon the primary key of another entity
pointer
field of data that can be used to locate a related field or row of data
calculated field
field that can be derived from other database fields
recursive foreign key
foreign key in a relation that references the primary key values of that same relation
