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AIS
Chapter 4
39
Accounting
Undergraduate 3
10/07/2010
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Term
4 Basic Requirements of a Relational Database
 Definition

  1. Every column in a row must be single valued
  2. Primary keys cannot be null
  3. Foreign keys, if not null, must have values that correspond to the value of a primary key in another table
  4. All nonkey attributes in a table should describe a characteristic about the object identified by the primary key
Term
Database management system (DBMS)
 Definition
acts as an interface between the database and the various application programs
Term
Database system
 Definition
the combination of the database, the DBMS, and the application programs that access the database through the DBMS
Term
database administrator (DBA)
 Definition
the person responsible for the database
Term
data warehouses
 Definition
very large databases
Term
data mining
 Definition
the process of analyzing data repositories for new knowledge about the company's data and business processes
Term
7 benefits of database technology
 Definition

  • data integration
  • data sharing
  • reporting flexibility
  • minimal data redundancy and data inconsistencies
  • data independence
  • central management of data
  • cross-functional analysis
Term
logical view of data
 Definition
how the user or programmer conceptually organizes and understands the data
Term
physical view of data
 Definition
refers to how and where the data are physically arranged and stored in the computer system
Term
record layout
 Definition
the physical location and layout of records used in an application program
Term
schema
 Definition
describes the logical structure of a database
Term
3 levels of schemas
 Definition

  • conceptual
  • external
  • internal
Term
conceptual-level schema
 Definition
the organizationwide view of the entire database.  it lists all data elements and the relationships among them
Term
external-level schema
 Definition
consists of a set of individual user views of portions of the database, each of which is also referred to as a subschema
Term
subschema
 Definition
individual user views of portions of the database
Term
internal-level schema
 Definition
provides a low-level view of the database
Term
data dictionary
 Definition
a key component of a DBMS which contains information about the structure of the database
Term
4 things the data definition language (DDL) is used to do
 Definition

  1. build the data dictionary
  2. initialize or create the database
  3. describe the logical views for each individual user or programmer
  4. specify any limitations or constraints on security imposed on database records or fields
Term
data manipulation language (DML)
 Definition
used for data maintenance, which includes such operations as updating, inserting, and deleting portions of the database
Term
data query language (DQL)
 Definition
used to interrogate the database. it retrieves, sorts, orders, and presents subsets of the database in response to user queries
Term
report writer
 Definition
a language that simplifies report creation
Term
data model
 Definition
an abstract representation of the contents of a database
Term
relational data model
 Definition
represents everything in the database as being stored in the form of tables
Term
relations
 Definition
the tables in a relational data model
Term
tuple
 Definition
each row in a relation
Term
primary key
 Definition
the attribute, or combination of attributes, that uniquely identifies a specific row in a table.
Term
foreign key
 Definition
an attribute in a table that is a primary key in another table (used to link tables)
Term
2 options for designing a relational database
 Definition

  • store all data in one uniform table
  • vary the number of columns
Term
disadvantages of storing all data in one uniform table
 Definition

  • creates a great deal of redundancy in terms of stored data
  • update anomaly
  • insert anomaly
  • delete anomaly
Term
update anomaly
 Definition
when changes (updates) to data values are not correctly recorded
Term
insert anomaly
 Definition
when there is no way to store information about prospective customers until they actually make a purchase
Term
delete anomaly
 Definition
when unintended results occur when deleting a row in the table (e.g. if a customer has made only one purchase, consisting of a single item, deleting that row from the table would result in the loss of all information about that customer)
Term
solutions to problems in storing data
 Definition
relational database
Term
relational database
 Definition
a set of tables used to store data
Term
entity integrity rule
 Definition
a non-null value for the primary key that indicates that a specific object exists and can be identified by reference to its primary key value
Term
referential integrity rule
 Definition
the use of foreign ensures the consistency of the database
Term
two approaches to database design
 Definition

  • normalization
  • semantic data modeling
Term
normalization
 Definition
an approach to database design that starts with the assumption that everything is initially stored in one large table.  a set of rules is then followed to decompose that initial table into a set of normalized tables
Term
objective of normalization
 Definition
to produce a set of tables in what is called third normal form
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