Outer Join (SQL)

Outer Join: all matching tuples are returned are returned (depending on type)

• Left Outer Join (SQL)

  Left Outer Join (LEFT OUTER JOIN): Keeps values from the left table even if they are not matched.

  SELECT E.name, S.fname
  FROM (
  					EMPLOYEE E
  	LEFT OUTER JOIN EMPLOYEE AS S
  				 ON E.super_ssn=S.ssn
  )

  This will match employees without supervisors.

  Link to original

• Right Outer Join (SQL)

  Right Outer Join (RIGHT OUTER JOIN): Keeps values from the right table even if they are not matched.

  SELECT E.name, S.fname
  FROM (
  		             EMPLOYEE E
  	RIGHT OUTER JOIN EMPLOYEE AS S
  				  ON E.super_ssn=S.ssn
  )

  This will match employees who are not supervising anyone.

  Link to original

• Full Outer Join (SQL)

  Full Outer Join (FULL OUTER JOIN): Keeps values from the both tables even if they are not matched.

  SELECT E.name, S.fname
  FROM (
  					EMPLOYEE E
  	FULL OUTER JOIN EMPLOYEE AS S
  				 ON E.super_ssn=S.ssn
  )

  This will match employees without supervisors and employees not supervising anyone.

  Link to original