VISUAL PRESENTATIONS FOR ER DIAGRAMS IN DBMS P

VISUAL PRESENTATIONS FOR ER DIAGRAMS IN DBMS P. KUTTI Mentor Department of Information Technology IIIT RK Valley campus, RGUKT-A. P 516330

Geometric Shapes � � � An entity–relationship model (ER model) is a systematic way of describing and defining a business process. . Rectangle: Represents Entity sets. Ellipses: Attributes. Diamonds: Relationship Set. Lines: They link attributes to Entity Sets and Entity sets to Relationship Set. Double Ellipses: Multivalued Attributes

Reflection Spot Activity � � � Which of the following indicates the maximum number of entities that can be involved in a relationship? (Time Slot: 07. 00) A) Minimum cardinality B) Maximum cardinality C) ERD D)Greater Entity Count (GEC) Answer: Option B

Lb. D for ER Diagrams in DBMS � � � Explanation: Cardinality ratio is the property of relationship set that indicates the ratio in which entities of different entity sets are related by relationship set or by itself. So, it is obvious that if cardinality increases then the ratio by which the different entities of the entity sets are related to each-other gets increased. Cardinality refers to the uniqueness of data values contained in a column. High cardinality means that the column contains a large percentage of totally unique values. Low cardinality means that the column contains a lot of “repeats” in its data range. With reference to the definition, “The number of occurrences of one entity that are associated with the number of occurrences in another entity are known as cardinality. ”

ER Diagram in DBMS Stu _Id Stu _Nam e Stu _Add Student COL ID Study In COL Name College

Conclussion � A Total participation of an entity set represents that each entity in entity set must have at least one relationship in a relationship set.

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