What are the various symbols used to draw an e-r diagram, Database Management System

Assignment Help:

What are the various symbols used to draw an E-R diagram? Explain with the help of an example how weak entity sets are represented in an E-R diagram.

Various symbols used to draw an E-R diagram

13_Symbol ER Diagram.png


Weak Entity Sets - An entity set that does not have a key attribute is called weak entity set. A weak entity must participate in an identifying relationship type with an owner or identifying entity type Entities are identified by the combination of:
• A partial key of the weak entity type
• The primary key of the identifying entity type

Example:
Suppose that a DEPENDENT entity is identified by the dependent's first name and birhtdate, and the specific EMPLOYEE that the dependent is related to. DEPENDENT is a weak entity type with EMPLOYEE as its identifying entity type via the identifying relationship type DEPENDENT_OF

1958_Dependents.png


Related Discussions:- What are the various symbols used to draw an e-r diagram

Define the unique constraints for the table client, Define the following co...

Define the following constraints for the table client. (i) BAL_DUE must be at least 1000. (ii) NAME is a unique key. (i)ALTER TABLE CLIENT ADD CONSTRAINT CLIENT_BAL_DUE_C1

Define average latency time, Define average latency time. The average l...

Define average latency time. The average latency time of the disk is one-half the time for a full rotation of the disk.

Object query language and odmg schema , (a)    Provide the description of t...

(a)    Provide the description of the following ODMG schema in the Object Definition Language (ODL). (b)   Based on the above object database, write the following queries i

Insert into command, INSERT INTO command : Values can be inserted fo...

INSERT INTO command : Values can be inserted for all columns or for the selected columns Values can be given by sub query. In place of values parameter substitution

Give expression in both tuple calculus and domain calculus, Consider the fo...

Consider the following relational schema: Doctor(DName,Reg_no) Patient(Pname, Disease) Assigned_To (Pname,Dname) Give expression in both Tuple calculus and Domain calculus for

Create a database for store company details, You group has been hired by  T...

You group has been hired by  TrainingrUs.com to keeps track of training revenues. TrainingrUS.com wants you to keep scheduling. COURSE table contains following information:

What is difference between primary index and secondary index, What is diffe...

What is difference between primary index and secondary index? Primary Index a) It is an ordered file whose records are of fixed length along with two fields. b) Only base

Traffic data management, This report identifies and outlines my CIS 499 pro...

This report identifies and outlines my CIS 499 project named Traffic Data Management  Systems (TDMS) .   My goal is to design a replica of all traffic issues to be implemented i

Describe the relational model, a) Distinguish between ‘database' and ‘Data...

a) Distinguish between ‘database' and ‘Database Management Systems (DBMS)'. b) List and briefly describe five potential benefits of the database approach compared to conventio

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd