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Basic Definitions

This learning sequence explores definitions such as data items, entities, attributes, records, files, and entity identifiers in databases.

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Basic Definitions

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  1. Basic Definitions Fundamentals of Databases Dr. Rashid Al_Zubaidy

  2. Basic Definitions Welcome: The first learning sequence “ Basic Definitions “ Present learning: We shall explore the following definitions: - Data-item name and value. - Key identifier. - Record and File.

  3. Basic Definitions • DATA A collection of incoming facts to the organization. Information Incoming facts Data processing data Output

  4. Basic Definitions • DATA A collection of incoming facts to the organization. DATA-ITEM NAME The context for a recorded data-item is often indicated by a name, such as date, name, age, etc. Information Incoming facts Data processing data Output

  5. Basic Definitions • GROUP ITEMS AND ELEMENTRY ITEMS A group item is a collection of closely related items of information. For example DATE usually have three parts, MONTH, DAY, YEAR, when any of there have no farther subdivision into meaning full parts they are called ELEMENTRY data-item else the called GROUP data-item or (Aggregate).

  6. Basic Definitions • AnENTITY Items about which we store information are referred to as Entities. An Entity may be Tangible object such as: A person (Employee), place (Amman), or thing (parts) An Entity may be Non Tangible, such as: An event (something happens at a particular time), customer-account, etc.

  7. Basic Definitions AN ATTRIBUTE An Entity has various properties which we may wish to record, so that we can recognize, remember, and describe it. These properties are called Attributes. For example: Attributes of human being include items such as: (height, weight, name, age, eye color, etc.) Attributes of car accident include items such as: (driver-name, time, location, cause of accident, etc.)

  8. Basic Definitions DATA-ITEM VALUE It is the specific quantative or qualitative values given to a specific data-item. For example: If ‘AGE’ is an attribute of some entity and it is equal to ’22’, then 22 is the related data value and it is quantative. And if ‘CITY’ is an attribute of some entity and it is ‘Baghdad’ then ‘Baghdad’ represent the data item value for data-item name CITY, and it’s qualitative.

  9. Basic Definitions • RECORD Is a collection of related data-item which share a common context about a particular entity.

  10. Basic Definitions • RECORD Is a collection of related data-item which share a common context about a particular entity. • FILE A file may be defined as a set of (Logical) records all of which related to a particular area of interest.

  11. Basic Definitions ENTITY IDENTIFIER It is necessary for the programmer or data administrator to be able to refer to a record relating to a given entity, and it is necessary for the computer to be able to identify it and have a means of finding it in the storage unit. For this purpose one of the attributes is usually designated an entity identifier.

  12. Basic Definitions ENTITY IDENTIFIER It is necessary for the programmer or data administrator to be able to refer to a record relating to a given entity, and it is necessary for the computer to be able to identify it and have a means of finding it in the storage unit. For this purpose one of the attributes is usually designated an entity identifier. For example the entity identifier of an employee would be EMPLOYEE-NUMBER.

  13. Basic Definitions ENTITY IDENTIFIER It is necessary for the programmer or data administrator to be able to refer to a record relating to a given entity, and it is necessary for the computer to be able to identify it and have a means of finding it in the storage unit. For this purpose one of the attributes is usually designated an entity identifier. For example the entity identifier of an employee would be EMPLOYEE-NUMBER. And the entity identifier of an account record would be the ACCOUNT-NUMBER.

  14. Basic Definitions ENTITY IDENTIFIER It is necessary for the programmer or data administrator to be able to refer to a record relating to a given entity, and it is necessary for the computer to be able to identify it and have a means of finding it in the storage unit. For this purpose one of the attributes is usually designated an entity identifier. For example the entity identifier of an employee would be EMPLOYEE-NUMBER. And the entity identifier of an account record would be the ACCOUNT-NUMBER. Some time more than attribute is required in order to identify a record. For example, to identify an airline flight record the FLIGHT-NUMBER and FLIGHT-DATE are needed.

  15. Basic Definitions • KEY Is an attribute or a set of attributes which the computer uses to identify a record.

  16. Basic Definitions • KEY • Is an attribute or a set of attributes which the computer uses to identify a record. • PRIMARY KEY • Is defined as that key used to uniquely identify one record. Such as ‘STUDENT-NUMBER’, ‘EMPLOYEE-ID’, etc.

  17. Basic Definitions CUSTOMER table

  18. Basic Definitions CUSTOMER table Data-item name (Attributes) (Fields)

  19. Basic Definitions CUSTOMER table Data-item name Data-item value

  20. Basic Definitions CUSTOMER table Primary key

  21. Basic Definitions CUSTOMER table Records . . Customer File

  22. Basic Definitions Summary: In this learning sequence, we discussed the basic definitions related the subject “database“.

  23. Basic Definitions END

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