Database

872 views

Published on

Published in: Technology
1 Comment
1 Like
Statistics
Notes
No Downloads
Views
Total views
872
On SlideShare
0
From Embeds
0
Number of Embeds
5
Actions
Shares
0
Downloads
46
Comments
1
Likes
1
Embeds 0
No embeds

No notes for slide

Database

  1. 1. DATABASE DESIGN SUBMITTED BY : SURBHI JAGGI NEELESH VAISH
  2. 2. FieldsA field is the physical implementation of a dataattribute. They are the smallest unit of meaningfuldata.A primary key is a field A descriptive field is anywhose values identify one other (nonkey) field thatand only one record in a file. stores business data.A secondary key is analternate identifier for arecord.A foreign key is a pointer toa record in a different file.
  3. 3. RecordsA record is a collection of fields arranged in apredefined format.  Fixed-length record structures  Variable-length record structuresA blocking factor is the number of logicalrecords included in a single read or writeoperation (from the computer’s perspective). 3
  4. 4. DBMS Environment SkillsInventory Profit Sharing DBMS • Skills DataInventory •Profit Sharing Data •Benefits DataEmployee BenefitsApplication
  5. 5. Objectives OfDatabase Controlled Redundancy Ease of learning and use Data Independence More Information at Low Cost Accuracy and Integrity Recovery From Failure Privacy and security Performance 5
  6. 6. Key Terms  Users View  Processing  Data Model  Data File 6
  7. 7. What is DBMS?“ In a Database Environment, a DBMS is the software that provides the interface between the data file on disk and the program that requests processing. ” 7
  8. 8. Some Important Terms DML – or ‘Data Manipulation Language’DML manipulates data, i.e. it specifies what is required DDL – or ‘Data Definition Language’DDL describes how the data is structured 8
  9. 9. Functions of a DBMS Storing, Retrieving and Updating data Creating program and data independence Enforcing Procedures for data integrity Reducing data redundancy Providing security facilities for defining users and enforcing authorizations Reducing Physical storage requirements by separating the logical and physical aspects of the database. 9
  10. 10. LOGICAL ANDPHYSICALVIEWS OF DATA
  11. 11. PHYSICAL VIEW OF DATA It is the way data exist in physical storage. It deals with how data stored, accessed, or related to other data in storage. 11
  12. 12. LOGICAL VIEW OF DATA what the data look like, regardless of how they are stored. The logical views are the user’s view, the programmer’s view, and the overall logical view, called a schema. 12
  13. 13. SCHEMAS It is the view that helps the DBMS (database management system) decide what data in storage it should act upon as requested by the application program. Example: Is the arrival and departure display at an airport. 13
  14. 14. SUBSCHEMAS It is the programmer’s (pilot’s) view. Many subschemas can be derived from one schema. Example: just as different pilots visualize different views of landing approach, although all (it is hoped) arrive at the sheduled time indicated on the CRT screen display (schema). 16
  15. 15. What is an ENTITY ??AN ENTITY IS A THING OR OBJECT OFIMPORTANCE ABOUT WHICH DATA MUST BECAPTURED. ALL THINGS ARENTENTITIES—ONLY THOSE ABOUT WHICHINFORMATION SHOULD BE CAPTURED. ANENTITY IS SOMETHING THAT EXISTSINDEPENDENTLY .
  16. 16. Cardinality
  17. 17. DATABASE NORMALIZATION Database normalization is a design technique by which relational database systems are structured in such a way as to make them less vulnerable to certain types of logical inconsistencies and anomalies. Tables can be normalized to varying degrees: relational database theory defines "normal forms" of successively higher degrees of stringency. 22
  18. 18. Data NormalizationAn logical entity (or physical table) is in first normal form if there are no attributes (fields) that can have more than one value for a single instance (record).An logical entity (or physical table) is in second normal form if it is already in first normal form and if the values of all nonprimary key attributes are dependent on the full primary key.An logical entity (or physical table) is in third normal form if it is already in second normal form and if the values of all nonprimary key attributes are not dependent on other nonprimary key attributes . 23
  19. 19. First Normal Form The criteria for first normal form :  A table must be guaranteed not to have duplicate records.  There must not be any repeating groups, ie, no attributes which occur a different number of times on different records. 24
  20. 20. R NO. NAME DOB SUBJECT GRADE 1 ABC 2 MARCH,1989 OS A BS A+ CONA B+ 2 DEF 25 DECEMBER,92 BS A ENGLISH AR NO. NAME DOB SUBJECT GRADE1 ABC 2 MARCH,1989 OS A1 ABC 2 MARCH,1989 BS A+1 ABC 2 MARCH,1989 CONA B+2 DEF 25 DECEMBER,92 BS A2 DEF 25 DECEMBER,92 ENGLISH A
  21. 21. Second Normal Form Criteria for second normal form :  The table must be in 1NF  None of the non-prime attributes of the table are functionally dependant on a part of a candidate key.  None of a 1NF’s candidate keys are composite. 26
  22. 22. R NO. NAME DOB1 ABC 2 MARCH,19892 DEF 25 DECEMBER,92R NO. SUBJECT GRADE1 OS A1 BS A+1 CONA B+2 BS A2 ENGLISH A
  23. 23. Third Normal Form Criteria for third normal form:  Table must be in 2NF.  There are no non-trivial functional dependencies between two non prime attributes. 28
  24. 24. SSN PNUMBER HOURS ENAME PNAME PLOCATIONSSN PNUMBER HOURS SSN ENAME PNUMBER PNAME PLOCATION
  25. 25. Roles of DatabaseAdministratorManaging data activitiesManaging database structureManaging DBMS 30

×