4. ER to Relational Mapping – 4marks

Question 1

The ordered steps (with instructions) in mapping from an ERD to relational schema are:

Answer 1

ORDERED STEPS: 
Acronym to remember: EWBBBMNS 
1.	Entity 
2.	Weak Entity 
3.	Binary 1:1 
4.	Binary 1: N (NB: FK from 1 side entity goes into N side entity) 
5.	Binary M:N  
6.	Multi-valued Attribute
7.	N-ary
8.	Super & Sub-classes (NB: EER only - relations for each super and subclass work for all situations) 

INSTRUCTIONS for all steps:

1. Create relation tables for ALL, EXCEPT STEPS 3 & 4 (1:1 & 1:N)
2. Define appropriate foreign keys for STEPS 3-7