Physical data independence: Any modification in the physical location of a table should not enforce modification at application level.
Also, set operations like Union, Intersection and minus should be supported. High level insert, update and delete rule: Relational Model should support insert, delete, update etc.View Updating Rule: Different views created for various purposes should be automatically updatable by the system.Comprehensive Data Sub-language Rule: A database should be accessible by a language supported for definition, manipulation and transaction management operation.Active Online Catalog: Structure of database must be stored in an online catalog which can be queried by authorized users.Systematic Treatment of NULL values: NULL value in database must only correspond to missing, unknown or not applicable values.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.Information Rule: Data stored in Relational model must be a value of some cell of a table.Foundation Rule: For any system that is advertised as, or claimed to be, a relational data base management system, that system must be able to manage data bases entirely through its relational capabilities.Codd which should be satisfied by relational model. Table 1 and Table 2 represent relational model having two relations STUDENT and STUDENT_COURSE.Ĭodd rules were proposed by E.F. Two NULL values in a relation are considered different from each other. NULL values: Values of some attribute for some tuples may be unknown, missing or undefined which are represented by NULL. STUDENT relation given below has 4 tuples. Tuple: Each row of a relation is known as tuple. For Example, domain of STUD_AGE can be from 18 to 40. are attributes of relation STUDENT.ĭomain of an attribute: The possible values an attribute can take in a relation is called its domain. Relational Instance: The set of values present in a relation at a particular instance of time is known as relational instance as shown in Table 1 and Table 2.Īttribute: Each relation is defined in terms of some properties, each of which is known as attribute. Challenges of database security in DBMS.Introduction to TimeStamp and Deadlock Prevention Schemes in DBMS.Graph Based Concurrency Control Protocol in DBMS.Two Phase Locking (2-PL) Concurrency Control Protocol | Set 3.Categories of Two Phase Locking (Strict, Rigorous & Conservative).Lock Based Concurrency Control Protocol in DBMS.Condition of schedules to View-equivalent.Precedence Graph For Testing Conflict Serializability in DBMS.Types of Schedules based Recoverability in DBMS.ISRO CS Syllabus for Scientist/Engineer Exam.ISRO CS Original Papers and Official Keys.GATE CS Original Papers and Official Keys.
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