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  3  Identify relationships between entities 

 The   

relationships

  between entities require identification of which fields are used to link the 

tables. For example, for each order a customer places we need to know which customer has 

placed the order and which product they have ordered. As is evident from  Figure   11.6   , the 

fields ‘customer ID’ and ‘product ID’ are used to relate the order information between the 

  Data  modelling 

  Entity 

  A grouping of related 

data, such as customer 

entity, implemented as 

a  table.   

  Database  table 

  Each  database  comprises 

several  tables.   

  Attribute 

  A  property  or 

characteristic of an entity, 

implemented as a field.   

  Field 

  Attributes  of  products, 

such as date of birth.   

  Record 

  A collection of fields for 

one instance of an entity, 

such as Customer Smith.