Joins
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This document discusses different types of joins in SQL, including inner joins, left joins, right joins, full joins, and unions. It provides examples of each type of join on tables of employee and order data, and explains how each join handles matching and non-matching rows from the left and right tables in the result set.
Joins
- 7. padding tuples from the left relation that did not match any from the right relation, as well as tuples from the right relation that did not match any from the left relation, and adding them to the result of the join.
- 15. Exercise !!!!!!
- 16. P_Id LastName FirstName Address City 1 Hansen Ola Timoteivn 10 Sandnes 2 Svendson Tove Borgvn 23 Sandnes 3 Pettersen Kari Storgt 20 Stavanger
- 17. O_Id OrderNo P_Id 1 77895 3 2 44678 3 3 22456 1 4 24562 1 5 34764 15
- 18. The INNER JOIN keyword returns rows when there is at least one match in both tables. If there are rows in "Persons" that do not have matches in "Orders", those rows will NOT be listed.
- 19. SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons INNER JOIN Orders ON Persons.P_Id=Orders.P_Id ORDER BY Persons.LastName
- 20. LastName FirstName OrderNo Hansen Ola 22456 Hansen Ola 24562 Pettersen Kari 77895 Pettersen Kari 44678
- 21. SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons LEFT JOIN Orders ON Persons.P_Id=Orders.P_Id ORDER BY Persons.LastName
- 22. The LEFT JOIN keyword returns all the rows from the left table (Persons), even if there are no matches in the right table (Orders).
- 23. LastName FirstName OrderNo Hansen Ola 22456 Hansen Ola 24562 Pettersen Kari 77895 Pettersen Kari 44678 Svendson Tove
- 24. The RIGHT JOIN keyword returns all the rows from the right table (table_name2), even if there are no matches in the left table (table_name1).
- 25. SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons RIGHT JOIN Orders ON Persons.P_Id=Orders.P_Id ORDER BY Persons.LastName
- 26. LastName FirstName OrderNo Hansen Ola 22456 Hansen Ola 24562 Pettersen Kari 77895 Pettersen Kari 44678 34764
- 27. The FULL JOIN keyword returns all the rows from the left table (Persons), and all the rows from the right table (Orders). If there are rows in "Persons" that do not have matches in "Orders", or if there are rows in "Orders" that do not have matches in "Persons", those rows will be listed as well.
- 28. SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons FULL JOIN Orders ON Persons.P_Id=Orders.P_Id ORDER BY Persons.LastName
- 29. LastName FirstName OrderNo Hansen Ola 22456 Hansen Ola 24562 Pettersen Kari 77895 Pettersen Kari 44678 Svendson Tove 34764
- 30. E_ID E_Name 01 Hansen, Ola 02 Svendson, Tove 03 Svendson, Stephen 04 Pettersen, Kari
- 31. E_ID E_Name 01 Turner, Sally 02 Kent, Clark 03 Svendson, Stephen 04 Scott, Stephen
- 32. SELECT E_Name FROM Employees_Norway UNION SELECT E_Name FROM Employees_USA
- 33. E_Name Hansen, Ola Svendson, Tove Svendson, Stephen Pettersen, Kari Turner, Sally Kent, Clark Scott, Stephen
- 34. SELECT E_Name FROM Employees_Norway UNION ALL SELECT E_Name FROM Employees_USA
- 35. SELECT E_Name FROM Employees_Norway UNION ALL SELECT E_Name FROM Employees_USA
- 36. E_Name Hansen, Ola Svendson, Tove Svendson, Stephen Pettersen, Kari Turner, Sally Kent, Clark Svendson, Stephen Scott, Stephen