translating from er to relationship schema adapted from juliana freire
Post on 19-Dec-2015
216 Views
Preview:
TRANSCRIPT
Translating from ER to Relationship Schema
Adapted from Juliana Freire
The easy partEntity relation with attributes
underlined field is keyRelationship -> relation?
special situations– Multi-valued and composite attributes– Weak entity sets– ISA relationships– Relations that result from an entity set and 1tomanyrelationship
Translating Many-to-Many
One to Many
One to Many answer
One – to- Many
One to Many with total participation
Why not a new relation?
Mapping many to many attribute
Throw the attributes onto the relationship table
1-to-many relationship with an attribute?
Add it to the 1 side
Translating Weak Entity Sets
Translating ISA relationship – as a tier
Translating ISA – one with all
Which one?
Participation Constraints
Splitting tables is always an option
Sample ERD
Equivalent Relational Schema
Translate This
Translation steps
top related