<commit_before># Database Management

A **database** is an organized collection of data (help people kepp trak of thinks). It is the collection of schemes, tables, queries, reports, views and other objects.

A **database management system** (DBMS) is a computer software application that interacts with the user, other applications, and the database itself to capture and analyze data. A general-purpose DBMS is designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs includes: [MySQL](https://www.mysql.com/), [PostgreSQL](http://www.postgresql.org/), [Microsoft SQL Server](http://www.microsoft.com/en-us/server-cloud/products/sql-server/features.aspx), [Oracle](https://www.oracle.com/database/index.html), [Sybase](www.sap.com/Database) and [IBM DB2](http://www-01.ibm.com/software/data/db2/).

- [Glossary](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#glossary)

## Context

- [Introduction](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#introduction)
  - [History of databases](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#history-of-databases)
  - [Data volume](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#data-volume)
- [Relational Model](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#the-relational-model)
- [Structured Query Language](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#structured-query-language) (SQL)
- [Entity Relationship Diagram](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#data-modeling-and-ert) (ERD)
- [Database Design](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#database-design)

## Introduction

The **first** patent for a **data storage device** was issued to <NAME> in 1884 for his punched card. Hollerith worked in the Census Office of the U.S. government. The census in the U.S. is conducted every ten years to count the population. The census of 1880 took eight years.

The importance of database processing increases every day because databases are used in information systems everywhere—and increasingly so. The **purpose of a database** is to help people keep track of things. Lists can be used for this purpose, but if a list involves more than one theme modification problems will occur when data are inserted, updated, or deleted.

**Relational databases** store data in the form of tables. Almost always, the tables are designed so that each table stores data about a single theme. Lists that involve multiple themes need to be broken up and stored in multiple tables, one for each theme. When this is done, a column needs to be added to link the tables to each other so that the relationship from a row in one table to a row in another table can be shown.

A **modification problem** is 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. 

An **anomaly** is defined as a abnormality or deviation from the expected. In a file system, an anomaly usually occurs when two or more files are merged to achieve data integration. Three possible modification **problems/anomalies** are:

- Insert problems — missing data
  - Insertion anomalies occur when adding data to a file that has redundancies.
- Update problems — inconsistent data
  - An update anomaly occurs when you make changes to records. 
- Delete problems — data loss.
  - Deletion anomalies occur when deleting a record from a file.

[**Structured Query Language**](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#structured-query-language) (SQL) is an international language for processing tables in relational databases. You can use SQL to join together and *display data stored in separate tables*, *create new tables*, and *query data from tables* in many ways. You can also use **SQL** to *insert*, *update*, and *delete* data.

The components of a **database system** are:

- Database
- Database management system (DBMS)
- Database applications (one or more)<commit_msg>Update database.md<commit_after># Database Management

A **database** is an organized collection of data (help people kepp trak of thinks). It is the collection of schemes, tables, queries, reports, views and other objects.

A **database management system** (DBMS) is a computer software application that interacts with the user, other applications, and the database itself to capture and analyze data. A general-purpose DBMS is designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs includes: [MySQL](https://www.mysql.com/), [PostgreSQL](http://www.postgresql.org/), [Microsoft SQL Server](http://www.microsoft.com/en-us/server-cloud/products/sql-server/features.aspx), [Oracle](https://www.oracle.com/database/index.html), [Sybase](www.sap.com/Database) and [IBM DB2](http://www-01.ibm.com/software/data/db2/).

- [Glossary](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#glossary)

## Context

- [Introduction](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#introduction)
  - [History of databases](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#history-of-databases)
  - [Data volume](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#data-volume)
- [Relational Model](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#the-relational-model)
- [Structured Query Language](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#structured-query-language) (SQL)
- [Entity Relationship Diagram](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#data-modeling-and-ert) (ERD)
- [Database Design](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#database-design)

## Introduction

The **first** patent for a **data storage device** was issued to *<NAME> in 1884 for his punched card*. Hollerith worked in the Census Office of the U.S. government. The census in the U.S. is conducted every ten years to count the population. The census of 1880 took eight years.

The importance of database processing increases every day because databases are used in information systems everywhere—and increasingly so. The **purpose of a database** is to help people keep track of things. Lists can be used for this purpose, but if a list involves more than one theme modification problems will occur when data are inserted, updated, or deleted.

**Relational databases** store data in the form of tables. Almost always, the tables are designed so that each table stores data about a single theme. Lists that involve multiple themes need to be broken up and stored in multiple tables, one for each theme. When this is done, a column needs to be added to link the tables to each other so that the relationship from a row in one table to a row in another table can be shown.

A **modification problem** is 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. 

An **anomaly** is defined as a abnormality or deviation from the expected. In a file system, an anomaly usually occurs when two or more files are merged to achieve data integration. Three possible modification **problems/anomalies** are:

- Insert problems — missing data
  - Insertion anomalies occur when adding data to a file that has redundancies.
- Update problems — inconsistent data
  - An update anomaly occurs when you make changes to records. 
- Delete problems — data loss.
  - Deletion anomalies occur when deleting a record from a file.

[**Structured Query Language**](https://github.com/valerysamovich/engineering/blob/master/docs/tutorials/database.md#structured-query-language) (SQL) is an international language for processing tables in relational databases. You can use SQL to join together and *display data stored in separate tables*, *create new tables*, and *query data from tables* in many ways. You can also use **SQL** to *insert*, *update*, and *delete* data.

The components of a **database system** are:

- Database
- Database management system (DBMS)
- Database applications (one or more)
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