Database Design - III

• Many-to-Many - For each row in the first table, there can be many rows in the second table, and for each row in the second table, there can be many rows in the first table.

• The relational model specifies two Integrity rules:

  • Entity integrity rule - Primary keys cannot contain null (missing) data.
  • Referential integrity rule - The database must not contain any unmatched foreign key values.

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