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What is the purpose of a database?
to help people keep track of things
What is the most commonly used type of database?
What is the difference in data and information?
Data: recorded facts and figures
- Information: knowledge derived from data
- data presented in a meaningful context
- data processed by summing, ordering, averaging, grouping, comparing or other similar operations.
- means of uniquiely identifying each row in a relation/table
- only one per relation
- may be a composite key
- ideal primary key is short, numeric and never changes
a primary key containing numbers that are automatically generated and assigned in the database itself
What is the difference between a form and a report?
one is input and one is output
a key that consists of two or more columns
a key that determines all other columns (attributes) in a relation
a combination of one or more columns that is used to identify rows in a relation
occurs when the value of one (set of) attribute(s) determines the value of a second (set of) attribute(s)
a determinant of a functional dependency that consists of more than one attribute
recorded facts and numbers
- knowledge derived from data
- data presented in a meaningful context
- data processed by summing, ordering, averaging, grouping, comparing, etc.
- has rows and columns like a spreadsheet
- breaks databases into related things
stores a characteristic common to all rows
a row containing (recording) data for a specific instance
an occurance of a thing
contains data about a particular occurance or instance of a thing of interest
- stores data and relationships
- records data in such a way that we can produce information from the data
What are the four typical components of a database system?
What's the fifth?
users, database application, database management system (DBMS), and the database
Structured Query Language (SQL)
Structured Query Language - an internationally recognized standard language that is understood by all commercial DBMS products.
Database management system - a computer program used to create, process, and administer the database.
a set of one or more computer programs that serves as an intermediary between the user and the DBMS
Basic functions of Application Programs:
- create and process forms
- process user queries
- create and process reports
- execute application logic
- control application
tells the database what the user needs to communicate - entry or input
where the database is asked a question and it returns an answer
the answer to a query in an unformatted display - generally columnar
answer generated by a query but instead of coming out in a result set, it comes out in a formatted display - through a report generator
a self-describing collection of integrated tables. Tables are integrated because they store data about the relationships between the rows of data, self-describing because it stores a description of itself.
Referential integrity constraints
rules that are enforced by the DBMS
Functions of a DBMS
- create database
- create tables
- create supporting structures (e.g., indexes)
- read database data
- modify (insert, update, or delete) database data
- maintain database structures
- enforce rules
- control concurrency
- provide security
- perform backup and recovery
the number of people hitting the database at the same time
The biggest issue with enterprise DBMS is:
concurrency - the number of people hitting the database at the same time (e.g. one user's work interfering with another user's work)
Examples of DBMS products:
- Microsoft Access - low end not for professionals
- Oracle Database
tables that store both data and the relationships among the data
data about data - tables contained within a database that describe the data within that database (table names, number of columns, primary keys, etc.)
- tables of user data
- stored procedures
- security data
- backup/recovery data
What are the three types of database design?
- 1. From existing data
- 2. New systems development
- 3. Database redesign
- some identifiable thing that users want to track (e.g. customers, computers, sales, etc.)
- provides the content that goes into the relation
the structure that will become the table in the database
Rules about relations:
- rows contain data about an entity
- columns contain data about attributes of the entity
- all entries in a column are of the same kind
- each column has a unique name
- cells of the table hold a single value
- the order of the columns is unimportant
- the order of the rows is unimportant
- no two rows may be identical
In order to have a referential integrity we have to have a minimum of __ tables.
- 2 tables = 1 referential integrity constraint
- 3 tables = 2 referential integrity constraints
- 4 tables = 3 referential integrity constraints etc.
A value cannot exist in a ________ key if it does not exist in the _______ key.
A value cannot exist in a foreign key if it does not exist in the primary key.