Entity Realtionships

Entity Realtionships

1. One - to - many

   • One record connects to many records
   • Foreign Key will exist on the "many" side of the table
   • Rules
     • Table on one side must have primary key
     • Table on many side must have a foreign key
     • data type and field size must match

2. One - to - one

   • one record connects to one record
   • Foreign Key can exist on either side
   • Rules
     • at least 1 of the tables must have a primary key
     • other table - have a primary key linking to A or foreign key linking to A
     • Data types must match

3. Many - to - many

   • many records connect to many records