Revision day 1

Database Mapping

• we can not delete or edit parent has child like edit one in the relationship 1 to M.
• Server=>DB=>Schema=>Objects(table)=>columns, rows.
• every column has domain=>data type.
• data type ensures quality, correct value(size),constrains & values.
• السهم بدايته تخرج من ال foreign key
• وراسه يذهب الي ال primary key.

ER-to-Relational Mapping

****Step 1: Mapping of Regular Entity Types

• Create table for each entity type -> if there is no 1-1 relationship mandatory from 2 sides
• Choose one of key attributes to be the primary key

Step 2: Mapping of Weak Entity Types

• Create table for each weak entity.
• Add foreign key that correspond to the owner entity type.
• Primary key composed of:
  • Partial identifier of weak entity
  • Primary key of identifying relation (strong entity)

Step 3: Mapping of Binary 1:1 Relation Types