How do the relations (tables) in SQL differ from the relations defined

How do the relations (tables) in SQL differ from the relations defined formally in Chapter 3? Discuss the other differences in terminology. Why does SQL allow duplicate tuples in a table or in a query result?

ER Model

Relational Model

Entity type

Entity relation

1:1 or 1:N relationship type

Foreign key(or relationship type)

M:N relationship type

Relationship relation and two foreign keys

n-ary relationship type

Relationship relation and n foreign keys

Simple Attributes

Attribute

Composite attributes

Set of simple component attribute

Multivalued attributes

Relation and foreign keys

Value set

Domain

Key attributes

Primary(or secondary) key