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Database is around with us for 30 years,Actually they are not the original nor the newest kind of data base.XML and object oriented data structures have evolved in modern years.Well still the relational database is the most common and popular kind of database widely available and hopefully stay in the same place for coming times.
Before starting SQL(structure Query Language) i think it is necessary to know some history about it.Oracle, SQL Server, and MySQL are very different from the databases used in first computerized database management.Hierarchical and network are the most commonly used database in 1970s.
Hierarchical Databases
Hierarchical Databases is the oldest database model dates back to 1960s it was managed by the IBM's IMS, which is still the same.Hierarchical model,the data is shaped in what is referred to as parent-child relationships in a visual this relations as a upside down tree like the picture below.
An important part to understand this concept is that a child element can have only one parent,but parent can have many child's.
In terms this relation between databases is known as one to many relationship.As an example,one department can have many employees.If you find hard to understand this structure,see Windows Explorer to look at the file structures of your computer.
You will see hierarchical structure is used to organize it.Until you,ve reached your destination you have to follow tree structure,this model of hierarchical got problems swell : a major one is data redundancy.This problem comes beacause hierarchical follows one to many relationship,and causing data duplication.For example, a hierarchical chart showing an employee who reports to more than one
supervisor would require duplicating that employee’s information.
Before starting SQL(structure Query Language) i think it is necessary to know some history about it.Oracle, SQL Server, and MySQL are very different from the databases used in first computerized database management.Hierarchical and network are the most commonly used database in 1970s.
Hierarchical Databases
Hierarchical Databases is the oldest database model dates back to 1960s it was managed by the IBM's IMS, which is still the same.Hierarchical model,the data is shaped in what is referred to as parent-child relationships in a visual this relations as a upside down tree like the picture below.
An important part to understand this concept is that a child element can have only one parent,but parent can have many child's.
In terms this relation between databases is known as one to many relationship.As an example,one department can have many employees.If you find hard to understand this structure,see Windows Explorer to look at the file structures of your computer.
You will see hierarchical structure is used to organize it.Until you,ve reached your destination you have to follow tree structure,this model of hierarchical got problems swell : a major one is data redundancy.This problem comes beacause hierarchical follows one to many relationship,and causing data duplication.For example, a hierarchical chart showing an employee who reports to more than one
supervisor would require duplicating that employee’s information.
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