DBMS - Relational Model
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The document discusses the relational database model. It begins by defining key terms like data, information, database, and DBMS. It then explains the relational model proposed by E.F. Codd, showing an example student database. Codd's rules for relational databases are listed. Types of database anomalies and keys like super keys, candidate keys, and foreign keys are also defined. The advantages of relational databases include structural independence and conceptual simplicity. Disadvantages include increased hardware needs and the potential for poor database design.
DBMS - Relational Model
- 1. Presented by – Ovais Bin Imtiaz, MFC(P) DBMS – Relational Model
- 2. Presented by – Ovais Bin Imtiaz, MFC(P) Some Basic Terms 1. Data :- Data are raw facts. The word raw indicates that the facts are unprocessed and doesn’t have meaning. It is used as input. 2. Information :- It’s meaningful form of data. Information is the result of processing raw data to reveal it’s meaning. 3. Database :- A collection of inter related data is called database. • A database is a shared , integrated computer structure that store a collection of end-user data and metadata. • A database can be of any size and complexity. • A database may be generated and maintained manually or it may be computerized.
- 3. Presented by – Ovais Bin Imtiaz, MFC(P) 4. Bit :- A single binary digit (0 or 1). 5. Character :- Multiple related bits are combined to form a character. 6. Field :- A character or group of characters that has a specific meaning. A filed is used to define and store data. 7. Record :- A logically connected set of one or more fields that describes a person, place, or thing. 8. File :- A collection of related record. 9. Schema :- Description of a database. 10. Instance :- Overall information stored in a database at a particular moment is called the instance of the database.
- 4. Presented by – Ovais Bin Imtiaz, MFC(P) 11. DBMS :- A Database Management System is a collection of programs that manage the database structure and controls access to the data stored in the database Its allows to • create databases; • insert , update and delete data; • sort and query data; • create form and reports. Examples of DBMS – Oracle, MySQL, SQLite, DB2 and MS Access
- 5. Presented by – Ovais Bin Imtiaz, MFC(P) Improved Data Sharing Improved Data security Minimized data inconsistency Improved Data Access Improved decision making Increased end-user productivity . Reduce application development time Role and Advantages of DBMS
- 6. Presented by – Ovais Bin Imtiaz, MFC(P) Railway Reservation Library Management System Banking Schools and colleges Social media sites Telecommunication Finance Online shopping Applications of DBMS
- 7. Presented by – Ovais Bin Imtiaz, MFC(P) What does Database Model mean? A database model is a type of data model that determines the logical structure of a database and functionally determines in which manner data can be stored, organized and manipulated. A database model :- shows the logical structure of a database; describe the relationships between different parts of the data; serves as blueprint for application developers and database administrators in creating a database
- 8. Presented by – Ovais Bin Imtiaz, MFC(P) STUDENT ROLL_NO NAME ADDRESS PHONE AGE 1 RAM DELHI 9455123451 18 2 RAMESH GURGAON 9652431543 18 3 SUJIT ROHTAK 9156253131 20 4 SURESH DELHI 9156243131 18 Relational Model was proposed by E.F. Codd in 1970 to model data in the form of relations or tables. Relational Model represents how data is stored in Relational Databases. A relational database stores data in the form of relations. Relational Model of DBMS Example :-
- 9. Presented by – Ovais Bin Imtiaz, MFC(P) Codd rules were proposed by E.F. Codd which should be satisfied by relational model. 1. Information Rule: Data stored in Relational model must be a value of some cell of a table. 2. Guaranteed Access Rule: Every data element must be accessible by table name, its primary key and name of attribute whose value is to be determined. 3. Systematic Treatment of NULL values: NULL value in database must only correspond to missing, unknown or not applicable values. 4. Active Online Catalog: Structure of database must be stored in an online catalog which can be queried by authorized users. 5. Comprehensive Data Sub-language Rule: A database should be accessible by a language supported for definition, manipulation and transaction management operation. 6. View Updating Rule: Different views created for various purposes should be automatically updatable by the system. 7. High level insert, update and delete rule: Relational Model should support insert, delete, update etc. operations at each level of relations. Also, set operations like Union, Intersection and minus should be supported. Codd Rules
- 10. Presented by – Ovais Bin Imtiaz, MFC(P) 8. Physical data independence: Any modification in the physical location of a table should not enforce modification at application level. 9. Logical data independence: Any modification in logical or conceptual schema of a table should not enforce modification at application level. For example, merging of two tables into one should not affect application accessing it which is difficult to achieve. 10. Integrity Independence: Integrity constraints modified at database level should not enforce modification at application level. 11. Distribution Independence: Distribution of data over various locations should not be visible to end-users. 12. Non-Subversion Rule: Low level access to data should not be able to bypass integrity rule to change data.
- 11. Presented by – Ovais Bin Imtiaz, MFC(P) An anomaly is an irregularity, or something which deviates from the expected or normal state. When designing databases, we identify three types of anomalies: Insert, Update and Delete. Anomalies in Relational Model STUDENT ROLL_NO NAME ADDRESS PHONE AGE BRANCH _CODE 1 RAM DELHI 9455123451 18 CS 2 RAMESH GURGAON 9652431543 18 CS 3 SUJIT ROHTAK 9156253131 20 ECE 4 SURESH DELHI 9156243131 18 IT BRANCH BRANCH_CO DE BRANCH_NAME CS COMPUTER SCIENCE IT INFORMATION TECHNOLOGY ECE ELECTRONICS AND COMMUNICATION ENGINEERING CV CIVIL ENGINEERING
- 12. Presented by – Ovais Bin Imtiaz, MFC(P) Insertion Anomaly in Referencing Relation: Insertion of a student with BRANCH_CODE ‘ME’ in STUDENT relation will result in error because ‘ME’ is not present in BRANCH_CODE of BRANCH. Deletion/ Updation Anomaly in Referenced Relation: If we try to delete tuple from BRANCH having BRANCH_CODE ‘CS’, it will result in error because ‘CS’ is referenced by BRANCH_CODE of STUDENT, but if we try to delete the row from BRANCH with BRANCH_CODE CV, it will be deleted as the value is not been used by referencing relation. It can be handled by following method: ON DELETE CASCADE: It will delete the tuples from REFERENCING RELATION if value used by REFERENCING ATTRIBUTE is deleted from REFERENCED RELATION. e.g., if we delete a row from BRANCH with BRANCH_CODE ‘CS’, the rows in STUDENT relation with BRANCH_CODE CS (ROLL_NO 1 and 2 in this case) will be deleted. ON UPDATE CASCADE: It will update the REFERENCING ATTRIBUTE in REFERENCING RELATION if attribute value used by REFERENCING ATTRIBUTE is updated in REFERENCED RELATION. e.g., if we update a row from BRANCH with BRANCH_CODE ‘CS’ to ‘CSE’, the rows in STUDENT relation with BRANCH_CODE CS (ROLL_NO 1 and 2 in this case) will be updated with BRANCH_CODE ‘CSE’.
- 13. Presented by – Ovais Bin Imtiaz, MFC(P) 1. Super key :- An attribute that uniquely identifies each row in a table. E.g. :- customer name and customer id. 2. Candidate key :- A minimal super key. A super key that does not contain a subset of attributes that is itself a super key. E.g. :- customer id 3. Primary Key :- A candidate key selected to uniquely identify all other attribute values in any given row. Cannot contain null entries 4. Unique Key :- A candidate key selected to uniquely identify all other attribute values in any given row. Can accept unique or null values 5. Foreign key :- An attribute in one table whose values must either match the primary key in another table or be null. Types of Keys in Relational Model
- 14. Presented by – Ovais Bin Imtiaz, MFC(P) Advantages of Relational Model Structural independence: In relational model, changes in the database structure do not affect the data access. Conceptual simplicity: Since the relational data model frees the designer from the physical data storage details, the designers can concentrate on the logical view of the database. Design, implementation, maintenance and usage ease: The relational database model achieves both data independence and structure independence making the database design, maintenance, administration and usage much easier than the other models. Ad hoc query capability: The query language of the relational database models structured query language or SQL makes ad hoc queries a reality. Using SQL the users can specify what information they want and leave the details of how to get the information to the database.
- 15. Presented by – Ovais Bin Imtiaz, MFC(P) Disadvantages of Relational Model Hardware overheads: For making things easier for the users, the relational database systems need more powerful hardware computers and data storage devices. So, the RDBMS needs powerful machines to run smoothly. Ease of design can lead to bad design: The users need not know the complex details of physical data storage. They need not know how the data is actually stored to access it. This ease of design and use can lead to the development and implementation of very poorly designed database management systems. 'Information island' phenomenon: As we have said before, the relational database systems are easy to implement and use. This will create a situation where too many people or departments will create their own databases and applications.
- 16. Presented by – Ovais Bin Imtiaz, MFC(P) Thanks