Chapter 1: Getting Started

modification problem
A data corruption or loss that occurs when a table uses one row to store facts about two or more themes. In this case, a deletion of a row can remove facts about two or more themes, leading to a loss in data, or a data change must be made in multiple rows to maintain data consistency. Finally, unless creation of a new row is allowed based on only one theme, it may be impossible to store needed data.
Possible types of modification problems (3)
1) Insert problems–missing data
2) update problems–inconsistent data
3) delete problems–data lost
null values
a row with incomplete values
When will modification problems result?
Whenever a list has data about two or more different things
relational database
Contains a collection of separate tables.
table
Holds data bout one and only one theme in most circumstances
modification actions
insert, update and delete
ID Column
This is used to assign a unique identifying number to each row of a table
SQL
Stands for Structured Query Language. It is used for combining, querying and processing sets of tables and the data in those tables. It could be used to recombine two or more tables into a new table.
database
A self-describing collection of related tables (or records), where self-describing means that the database contains a description of itself within itself
Components of a Database
1) User data
2) Metadata
3) Indexes and other overhead data
4) Application metadata
Importance of the quality of a database to be self-describing
It is important for a database to be self-describing so that there is always a way to know the database’s structure and contents. Without the self-description, it would not be possible to know what’s in the database
Database Management System (DBMS)
A computer program used to create, process and administer the database. It receives requests encoded in SQL and translates those
database applilcation
A set of one or more computer programs that serves as an intermediary between the user and the DBMS. Application programs read or modify data by sending SQL statements to the DBMS.
metadata
Data about the structure of a database. Examples include the names of tables, the names of columns and the tables to which they belong, indexes, columns, etc.
Commercial DBMS products
Microsoft SQL server
Oracle Corporation’s My SQL
Oracle Corporation’s Oracle Database
IBM’s DB2
Four components of a database system
1) User
2) Database application
3) DBMS
4) database
Use of an Index
Used to improve database performance
Application metadata
Application metadata are the data that describe the application elements. Examples are reports and forms.
Purpose of a DBMS
The purpose of this system is to create, process and administer databases
Specific functions of a DBMS
Create databases, create tables, create supporting structures (indexes, etc.), read database data, modify (insert, update or delete) database data, maintain database structures, enforce (business) rules, control concurrency, provide security, perform back-up and recovery
referential integrity constraint
A rule that before a possible key of value of one table can be placed in a second table as a linking value, the value must exist in the first table before it is used in the second table.

Ex: OwnerPhone in PET must exist in OwnerPhone in OWNER

A DBMS is a problem for defining, processing and administering a database. A database is simply a file of data consisting of user data, metadata, indexes and other overhead data and application metadata.
Difference Between DBMS and databse
Create a process forms
Process user queries
Create and process reports
Execute and application logic
Control the application
Functions of a database application
Main differences are in size and complexity. Application in DBMS like Microsoft Access. Enterprise-class database shave concurrent users, may need to run 24/7 and may have many different applications and application types
Main Differences between a personal database system and an enterprise-class database system
Hiding complexity makes it easier for users to learn and use the product. But, the problem with hiding database technology (and with using lots of wizards to accomplish database design tasks) is that you never understand what is being done on your behalf.
Advantages and disadvantages of hiding complexity from the user in a DBMS
concurrency
Ensuring the one user’s work does not inappropriately interfere with another user’s work
NoSQL
A database that does not use SQL. Or a nonrelational database.