▪︎Data hierarchy refers to the systematic organization of data, often in a hierarchical form.
▪︎Data organization involves characters, fields, records, files and so on.
▪︎A data field holds a single fact or attribute of an entity. Consider a date field, e.g. "September 19, 2004". This can be treated as a single date field, or 3 fields, namely, month, day of month and year. A record is a collection of related fields. An Employee record may contain a name field, address fields, birthdate field and so on.
▪︎A file is a collection of related records. If there are 100 employees, then each employee would have a record and the collection of 100 such records would constitute a file.
▪︎Files are integrated into a database. This is done using a Database Management System. If there are other facets of employee data that we wish to capture, then other files such as Employee Training History file and Employee Work History file could be created as well.
▪︎The above is a view of data seen by a computer user. The above structure can be seen in the hierarchical model, which is one way to organize data in a database.
▪︎This concept is a starting point when trying to see what makes up data and whether data has a structure.
Purpose of the Data Hierarchy:
▪︎Data hierarchy" is a basic concept in data and database theory and helps to show the relationships between smaller and larger components in a database or data file.
▪︎It is used to give a better sense of understanding about the components of data and how they are related.
Components:
1)Bit – is the smallest piece of data.
2)Byte – 8 or 16 bits representing a character.
3)Field – Any group of related bytes, identified by user.
4)Record – Groups related fields.
5)File – Group of related records, data used/generated by specific application program.
6)Database – Group of related files, interconnected at various levels, giving users flexibilityof access to stored data.
Levels of data Hierarchy:
There are three levels of data Hierarchy:
1)Attribute:
▪︎This is the most basic unit of data.
▪︎It is the smallest piece of information collected when capturing data.
▪︎Each attribute represents a specific and unique property or characteristic of an entity in the database.
▪︎A set of attributes of an entity effectively describe that entity. When translating the design into a relational database, each attribute becomes a column.
2)Record:
▪︎A data field holds a single fact or attribute of an entity.
▪︎A record is a collection of related fields.
▪︎An Employee record may contain a name field(s), address fields, birthdate field and so on.
▪︎A file is a collection of related records.
3)File:
▪︎A file is a collection of related records.
▪︎If there are 100 employees, then each employee would have a record (example :called Employee Personal Details record) and the collection of 100 such records would constitute a file (in this case, called Employee Personal Details file). Files are integrated into a database.
Advantages:
▪︎Manages large amounts of data.
▪︎Express the relationships between information.
▪︎Many children per parent.
▪︎Distribute data in terms of relationships.
▪︎Improve data sharing.
Disadvantages:
▪︎Data must be organized in a hierarchical way without compromising the information.
▪︎Lack structural independence.
▪︎Many too many relationships not supported.
▪︎Data independence.
▪︎Navigation system is complex.
