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One-to-one relationship:
For every 1:1 relationship type R in the ER diagram including two entities E1 and E2 we take one of entities (say E1) preferably with total participation and add primary key attribute of one more entity E2 as a foreign key attribute in the table of entity (E1). We will also have all the simple attributes of relationship type R in E1 if any.
For instance, the DEPARTMENT relationship has been extended to contain head-Id and attribute of the relationship. Please note we will maintain information in this table of only present head and Date from which s/he is the head.
There is one Head_of 1:1 relationship among FACULTY and DEPARTMENT. We select DEPARTMENT entity having total participation and add primary key attribute ID of FACULTY entity as a foreign key in DEPARTMENT entity named as Head_ID. Now the DEPARTMENT table will be as follows:
DEPARTMENT
D_NO
D_NAME
Head_ID
Date-from
Physical Database Design Issues The database design includes the process of logical design with the use of E-R diagram, normalisation, etc., followed by the physical design.
If the deletion violates referential integrity constraint, then three alternatives are available: Default option: - refuse the deletion. It is the job of the DBMS to describ
a. Construct a query around any one of the functional divisions you made in 4a such that if executed in the distributed design of 4 would require reconstruction of at least two ho
Domain Constraints Domain constraints are primarily formed for defining the logically correct values for an attribute of a relation. The relation allows attributes of a relatio
What is data model? Explain object based and record based data models? Ans: A data model is an abstract model in which describes how data is represented and accessed. (i)
Modify a sequence: ALTER SEQUENCE SEQSS INCREMENT 2 MAXVALUE 3000; Removing a sequence: DROP SEQUENCE SEQSS;
In E-R Diagram how relationship type is represented ? In E-R Diagram relationship type is represented as a Diamond.
intent locking
What is Candidate Key Super Key or Candidate Key: It is such an attribute of a table that can uniquely recognize a row in a table. Generally they have unique values and can n
Group By clauses • It is used to group database tuples on the basis of definite common attribute value like as employees of a department. WHERE clause still can be used
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