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Explain the conventions for displaying an ER schema as an ER diagram?
An E-R Diagram scheme might describe certain constraints to that the contents of a database must conform.
Mapping Cardinalities: Express the number of entities to that another entity can be related through a relationship. For binary relationship sets among entity sets A and B, the mapping cardinality must be one of:
1. One-to-one: An entity in A is related along with at most one entity in B, and an entity in B is related with at most one entity in A. 2. One-to-many: An entity in A is related along with any number in B. An entity in B is related with at most one entity in A. 3. Many-to-one: An entity in A is related with at most one entity in B. An entity in B is associated with any number in A. 4. Many-to-many: Entities in A and B are related along with any number from each other.
The suitable mapping cardinality for a particular relationship set depends on the real world being modeled. Cardinality ratios for binary relationships are represented on ER diagram through displaying 1,M, N etc. on the diamonds.
Existence Dependencies: if the existence of entity X depends on the existence of entity Y, then X is said to be existence dependent on Y.
Let consider the given partial relation EMP. Let us make some sub-queries for them EMPNO ENAME JOB SAL DEPTNO 7566
These are interactive interfaces, graphical that hide the difficulty of the DBMS and query language behind an intuitive, simple to understand, and convenient interface. This permit
explain thee diffrent types of data models
explain normalization,and give the examples 1NF,2NF,3NF,BCNF.AND FUNCTIONAL DEPANDENACY AND DECOMPOSITION TECHNIQUES.
Horizontal Fragmentation- Horizontal fragmentation groups together the tuples in a relation that are collectively used by the main transactions. A horizontal fragment is produced b
Analyzing Association Traversal Association Traversal shall be understood properly for the association design explanation. Analyzing association traversal means analyzing tra
What is nested relational model? The nested relational model is an extension of relational model in which domains might be either atomic or relation valued.
WHAT IS DSS? WRITE ITS REQUIREMENTS.
Example- Search the salary of employees who are not 'ANALYST' but get a salary below than or equal to any people employed as 'ANALYST'. SELECT EMPNO, ENAME, JOB, SAL FROMEMP
Explain CNT in the respects of QBE ? CNT: It is one of the aggregation commands given in QBE. It is used to identify number of tuples
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