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Relational Model (Mapping ERM to relational database (Step 7:…
Relational Model
Mapping ERM to relational database
Step 1: Identify strong/weak entity
Primary Key
Foreign Key
Step 2: Identify relationship type (1:1, 1:*, many:many)
Step 3: Identify associate attributes
simple/composite attributes
single/multi-valued attributes
derived attributes
Step 4: (1:*) Relationships
End with 1 is parent
End with * is child
Step 5: Binary (1:1)
Option A (mandatory participation on both sides)
Option B (mandatory participation on one side)
Option C (optional participation on both sides)
Step 6: Unary (Recursive) 1:1
Same with step 4
Step 7: Superclass/subclass relationship
{Mandatory, and}
{Mandatory, or}
{Optional, and}
{Optional, or}
Step 8: (many:many) relationships
Relation Keys
Superkey
Candidate Key
Primary Key
Alternate Keys
Foreign Key
Relational Integrity
Null - attribute is unknown
Entity integrity
Referential integrity
Enterprise constraints
Views
Base Relation
View
Definition - table with columns and rows
Column header/field = attribute
Row = tuple
Column value = domain
Number of tuple = cardinality
Number of attribute = degree