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Describe the two alternatives for specifying structural constraints on relationship kinds?
Relationship kinds have certain constraints in which limit the possible combination of entities that might participate in relationship. An example of a constraint is in which if we have the entities Doctor and Patient, the organization might have a rule that a patient cannot be seen through more than one doctor. This constraint needs to be elaborates in the schema. There are two major kinds of structural relationship constraints on: cardinality ratio, and participation.
Natural Join : It is the similar like Equi join except one of the duplicate columns is removed in the result table. The natural join is the most usually used form of join operation
Database Recovery And Security Introduction In this part we will introduce two main issues relating to database management systems. A computer system suffers from dissi
Q. Describe how an ER schema can be represented by relation schemas and constraints arising from ER design can be mapped to constraints on a relation schema. The entity rela
01a_Broadway_LastFirst_yyyy-mm-dd Capstone Exercises You work as a production assistant in the office of the Green Man Theatre. One of your duties is to maintain the company datab
What is foreign key? A relation schema r1 derived from an ER schema may contain among its attributes the primary key of another relation schema r2.this attribute is known as a
Types of Data fragmentation
To eliminate duplicate rows (distinct operator) Example: SELECT DISTINCT DEPTNO FROM EMP;
What are three components of the schema architecture proposed by ANSI/SPARC? The three component schema architecture proposed by ANSI/SPARC is as given below: External sche
Design a gennalization and specialization hierarchy for an automobile sales company
Increased overheads on update : On the drawbacks side, it will need the system to ensure that all replicas of a relation are consistent. This shows that all the replicas of the rel
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