Elementary Data Organization
Data: The term data means a value or set of values.
—For example, marks of students, figures obtained during polling etc.
Data item: A data item means a single unit of values.
—For example, roll number, name, address etc.
Group item: Data items that can be divided into sub items.
—For example:
Name
First Name
Middle Name
Last Name
Elementary item: Those items that can not be divided
—For example: Age, Gender
Entity: Entity is something that has certain qualities, characteristics, properties or attributes that may contain some values.
—For example, Student is an entity. The attributes of student may be roll number, name, address, etc,. The values of these attributes may be 100, abc, House No:133-A.
Entity Set: An entity set is a group of or set of similar entities.
—For example, employees of an organization, students of a class etc.
Information: When the data are processed by applying certain rules, new processed data is called information.
The data are not useful for decision making whereas information is useful for decision making.
Field: It is a single elementary unit of information representing an attribute of an entity.
—For example, 1, 2, 3, 4….etc are represented by a single unit called roll number field.
Record: Record is a collection of field values of a given entity.
—For example, roll number, name, address etc of a particular student.
File: File is a collection of records of the entities in a given entity set.
—For example, file containing records of students of a particular class.
Data Base: Collection of files
Relational Database: is a database that stores information about both the data and how it is related
Key: A key is one or more field(s) in a record that take(s) unique values and can be used to distinguish one record from the others
Data: The term data means a value or set of values.
—For example, marks of students, figures obtained during polling etc.
Data item: A data item means a single unit of values.
—For example, roll number, name, address etc.
Group item: Data items that can be divided into sub items.
—For example:
Name
First Name
Middle Name
Last Name
Elementary item: Those items that can not be divided
—For example: Age, Gender
Entity: Entity is something that has certain qualities, characteristics, properties or attributes that may contain some values.
—For example, Student is an entity. The attributes of student may be roll number, name, address, etc,. The values of these attributes may be 100, abc, House No:133-A.
Entity Set: An entity set is a group of or set of similar entities.
—For example, employees of an organization, students of a class etc.
Information: When the data are processed by applying certain rules, new processed data is called information.
The data are not useful for decision making whereas information is useful for decision making.
Field: It is a single elementary unit of information representing an attribute of an entity.
—For example, 1, 2, 3, 4….etc are represented by a single unit called roll number field.
Record: Record is a collection of field values of a given entity.
—For example, roll number, name, address etc of a particular student.
File: File is a collection of records of the entities in a given entity set.
—For example, file containing records of students of a particular class.
Data Base: Collection of files
Relational Database: is a database that stores information about both the data and how it is related
Key: A key is one or more field(s) in a record that take(s) unique values and can be used to distinguish one record from the others
There are three cases:
Case 1:
When more
than one field may have unique values. In that case, there exist multiple keys,
but at a time we use only one field as a key, called primary key. The other
key(s) are called as alternate key(s).
Case 2:
There is
no field that has unique values.
Then a combination of two or more fields can be used to form a key. Such a key is called composite key.
Then a combination of two or more fields can be used to form a key. Such a key is called composite key.
Case 3:
There is
no possibility of forming a key from the within the record. Then an extra field
can be added to the record that can be used as a key.
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