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What type of join is needed when you wish to include rows that do not have matching values?

  • A.Equi-join
  • B.Natural join
  • C.Outer join
  • D.All of the above.

Answer: C

Correct answer: Outer join

An outer join keeps the rows that have no match on the other side and fills the missing columns with nulls. Equi-joins and natural joins discard them, so a customer with no orders would simply disappear - which is precisely the case an outer join exists to report.

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