Rdbms
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The document discusses relational database management systems (RDBMS). It describes some key disadvantages of file processing systems like data redundancy and inconsistency. An RDBMS uses a database, DBMS, and application programs to allow for data storage in tables/relations with rows and columns. The document outlines important aspects of RDBMS like data models, database languages, database administrators, keys, relationships, and normalization.
![Second Normal Form (2NF)
A relation is said to be in 2NF if it is in 1NF and
All non-prime attributes are fully functionally dependent on candidate key
Consider a relation savings_deposit having the fol owing structure:-
Saving_deposit (name, addr, acc_no, amt )
With the fol owing FDs :
name Add
name, acc_no addr
Here [name, acc_no ] is the candidate key and addr and amt are the non
prime attributes.
Among the non-prime attributes amt depends on [name, acc_no ] whereas
addr depends
on name only.
Note that due to FD name
Address causing redundancy.
addr every tuple with the same name will contain the same
This redundancy arises because a non-prime attribute like address is
dependent on an attribute](https://image.slidesharecdn.com/rdbms-141101103151-conversion-gate01/85/Rdbms-38-320.jpg)
Rdbms
- 1. Relational Database Management System
- 2. Relational Database Management System DATA DATABASE DBMS/RDBMS Information
- 3. File Processing System Database (Information in Files Format) Application Programs (Programs Written in C Pascal etc.) File System (Data Structure File Handling)
- 4. Disadvantages of FPS Data Redundancy and Inconsistency Difficulty in accessing data Data isolation Integrity Problems Atomicity Problems Concurrent-access anomalies Security Problems
- 5. Data Redundancy and Inconsistency Name Address ABC Bhiwani DEF Delhi AccNo Name Address 1002 ABC Bhiwani 1005 DEF Jaipur Customer Information Saving Account
- 6. Difficulty in accessing data Application Programs (Programs Written in C Pascal etc.) File System (Data Structure File Handling) Database (Information Storage in Files Format) Manager Requirement
- 7. Requirements of a DBMS • A mechanism for specification of data and its dependencies (Integrity Constraints) in an integrated fashion. • Prevention of redundancy and inconsistency. • Provision of adequate security and access-rights. • Mechanism for concurrency control. • Mechanism for recovery from failure. Additionally any DBMS must provide • Schemes for specification of procession rules or application Programs. • Efficient techniques for storage and retrieval of data from the secondary
- 8. D B M S File Manager Secondary Storage A DBMS has two major components, namely Structure of Database is called Database Schema. Instance, which is a state of the database with the actual data loaded. A set of software tools/programs which access, update and process the database, called the query and update-mechanism.
- 9. Data Independence The ability to modify a schema definition in one level without affecting a schema definition in the next higher level is called data independence. Physical data independence Logical data independence Create table emp (empno number(10),------,-- ------);
- 10. Data Models A Data Model is a mechanism for describing the data, their interrelationships and the constraints. Object-based Conceptual models. Entity-Relationship model Record-based models. Relational Model Network Model Hierarchical Model Physical data models.
- 11. The E-R Model Entities : An entity is a distinct clearly identifiable object of the database e.g Book Attribute : Each Entity is characterized by a set of attributes e.g. Acc.No. Entity Set : Set of all entities having attributes of the same type. Relationships : A relationship is a mapping between entity sets. Acc_No Title Acc_No Card_No Name Book Borrowed_By USERS ____
- 12. Hierarchical Model This is special kind of a network model where the relationship is essentially a tree-like structure. Hospital Wards Units Patient Doctors Nurses Cardiology Skin
- 13. Physical Data Models Physical data models are used to describe data at the lowest level. In contrast to logical data models, there are few physical data models In use. Two of the widely known ones are the Unifying model and frame-Memory model. Database Languages Database Languages Data-Definition Data-Manipulation Data-Control Create Table Test ( Title Varchar2(20), -------- ,-------); Update Insert Delete Query GRANT Connect, Resource TO x User
- 15. Database Administrator Roles of DBA • Schema Definition • Storage structure and access-method definition • Schema and Physical-organization modification • Granting of authorization for data access • Integrity-constraint specification Terms • Simple and Composite Attributes • Single-valued and Multivalued Attributes • Null Attributes • Derived Attributes • Existence Dependencies •Weak Entity Set and Strong Entity Set
- 16. Weak Entity Set
- 18. Keys Keys Candidate Key Secondary Key Foreign Key Primary Key Alternate Key Composite Key
- 19. Mapping Cardinalities Mapping cardinalities, or cardinality ratios, express the number of entities to which another entity can be associated via a relationship set. For a binary relationship set R between entity sets A and B, the mapping Cardinality must be one of the following A B A B One to One One to Many
- 20. A B A B Many to One Many to Many
- 21. More on E-R Diagrams Company Owns Multiple Relationships between Leased Same entity set Vehicle Manager Staff Reports to Subordinate Circular Relationship
- 28. The Relational Algebra The relational algebra is a procedural query language. Fundamental Operations select (unary) project (unary) rename (unary) Fundamental Operations cartesian product (binary) union (binary) set-difference (binary) Several other operations, dened in terms of the fundamental operations: set-intersection natural join division assignment Operations produce a new relation as a result.
- 29. Formal Definition of Relational Algebra
- 32. The Cartesian Product Operation
- 33. The Union Operation The Set Difference Operation
- 34. Relational Calculus Relational Calculus is a nonprocedural Query language Tuple Relational Calculus Uses Tuple variables which take values of an entire tuple Domain Relational Calculus Uses Domain variables which takes values from an attribute
- 36. Normalization Normalization is a process of removing redundancy using functional Dependencies. To reduce redundancy it is necessary to decompose a relation into a number of smaller relations. There are several normal Forms. -First Normal Form (1 NF) -Second Normal Form (2 NF) -Third Normal Form(3 NF) -Boyce-Codd Normal Form (BCNF)
- 37. First Normal Form (1NF) This normal form says that all attributes are simple. An attribute is said to be simple if it does not contain any subparts. An attributes which contains subparts is called complex attributes. F_name L_name C_addr City State Zip Name
- 38. Second Normal Form (2NF) A relation is said to be in 2NF if it is in 1NF and All non-prime attributes are fully functionally dependent on candidate key Consider a relation savings_deposit having the fol owing structure:- Saving_deposit (name, addr, acc_no, amt ) With the fol owing FDs : name Add name, acc_no addr Here [name, acc_no ] is the candidate key and addr and amt are the non prime attributes. Among the non-prime attributes amt depends on [name, acc_no ] whereas addr depends on name only. Note that due to FD name Address causing redundancy. addr every tuple with the same name will contain the same This redundancy arises because a non-prime attribute like address is dependent on an attribute
- 39. Third Normal Form (3NF) A relation is said to be in 3NF and non-prime attributes are not dependent On each other. Consider the relation – s_by ( s_name, item, price, gift_item ) With FDs s_name, item price Price gift_item Here al prime attributes are ful y functional dependent on candidate keys, the Non-prime attribute gift-item is also ful y functional dependent on the non-prime Attribute price. This create redundancy because every price value there is a fixed Gift item. We shal have to impose the additional restriction that no non-prime attribute can Be functional y dependent on another non-prime attributes.
- 40. Boyce-Codd Normal Form (BCNF)