Left and right joins, PL-SQL Programming

Left and Right Joins

LEFT OUTER JOIN can be used when you want to retrieve the data from the main table (table1) even if there is no match in other tables (table_2, table_3....). While RIGHT OUTER JOIN is used to retrieve the data the from all other tables (table_2, table_3...) even if there is no match in the main table. As an example, in our classicalmodels sample database, when the company wants to establish a new office, the SQL script to insert a new office to the databse as follows:

INSERT INTO classicmodels.offices

(officeCode, city, phone, addressLine1, addressLine2, state, country, postalCode, territory)

VALUES  ('8', 'Boston', '+1 215 837 0825', '1550 dummy street', 'dummy address', 'MA', 'USA', '02107', 'NA')

At this time, the company hasn't hired any new employees yet, so the new office does not have any employees. If we want to know which employees belong to what offices and all the offices of the company, we can use RIGHT JOIN as follows:

SELECT firstname,

lastname,

addressLine1

 FROM employees as e  RIGHT OUTER JOIN offices as o

 ON o.officeCode = e.officeCode

The Right join on offices will cause all records from the offices table (the table on the right in the join stmt) to display, even if there is not a corresponding record in the employees table. Notice the last record contains null values for the first and last name values pulled from employees table. This is because there are no records in the employees table with an office code of 8 (the boston office we just added to the office table.)

 +-----------+-----------+--------------------------+

| firstname | lastname  | addressLine1             |

+-----------+-----------+--------------------------+

| Mary      | Patterson | 100 Market Street        |

| Diane     | Murphy    | 100 Market Street        |

| Jeff      | Firrelli  | 100 Market Street        |

| Anthony   | Bow       | 100 Market Street        |

| Leslie    | Jennings  | 100 Market Street        |

| Leslie    | Thompson  | 100 Market Street        |

| Julie     | Firrelli  | 1550 Court Place         |

| Steve     | Patterson | 1550 Court Place         |

| FoonYue  | Tseng     | 523 East 53rd Street     |

| George    | Vanauf    | 523 East 53rd Street     |

| Gerard    | Bondur    | 43 Rue JouffroyD'abbans |

| Loui      | Bondur    | 43 Rue JouffroyD'abbans |

| Gerard    | Hernandez | 43 Rue JouffroyD'abbans |

| Pamela    | Castillo  | 43 Rue JouffroyD'abbans |

| Martin    | Gerard    | 43 Rue JouffroyD'abbans |

| Mami      | Nishi     | 4-1 Kioicho              |

| Yoshimi   | Kato      | 4-1 Kioicho              |

| William   | Patterson | 5-11 Wentworth Avenue    |

| Andy      | Fixter    | 5-11 Wentworth Avenue    |

| Peter     | Marsh     | 5-11 Wentworth Avenu    |

| Tom       | King      | 5-11 Wentworth Avenue    |

| Larry     | Bott      | 25 Old Broad Street      |

| Barry     | Jones     | 25 Old Broad Street      |

| NULL      | NULL      | 1550 dummy street        |

+-----------+-----------+--------------------------+

24 rows in set (0.00 sec)

As you can see, the RIGHT JOIN get the all the data from second table (offices) and data from the first table even the condition does not match.

Posted Date: 2/16/2013 8:17:36 AM | Location : United States







Related Discussions:- Left and right joins, Assignment Help, Ask Question on Left and right joins, Get Answer, Expert's Help, Left and right joins Discussions

Write discussion on Left and right joins
Your posts are moderated
Related Questions
Enrolment was split - SQL Example shows how relvars IS_CALLED and IS_ENROLLED_ON can be derived from the original ENROLMENT relvar, using projection in the initial assignment

Functions The function is a subprogram which can take parameters and be invoked. Normally, you can use a function to calculate a value. The function has 2 sections: the specifi

MILLER-UREY' S EXPERIMENTAL PROCEDURES - They recreated the probable conditions on the primitive earth in the laboratory. An atmosphere containing hydrogen, ammonia, me

THEO R Y OF ETERNITY OF LIFE (PRAYER - 1880) - The theory of eternity of life, also called the steady-state theory , states that life has ever been in existence as at presen

write the program for traffic control system with 10 second, 15 secod, and 20 second delay

At times, customers make mistakes in submitting their orders and call to cancel the order. Brewbean’s wants to create a trigger that automatically updates the stock level of all pr

UNION without CORRESPONDING - SQL The use of UNION without CORRESPONDING. Example is merely by omitting CORRESPONDING, but only because the operands have identical SELECT clau

NULL Statement The NULL statement clearly specifies in action; it does nothing other than to pass control to the next statement. It can, though, improve the readability. In a

Using Aliases The Select-list items fetched from a cursor related with the %ROWTYPE should have simple names or, if they are expressions, should have aliases. In the example bel

Type versus Representation Confusion in SQL This describes how a value might have two or more distinct representations. For example, user-defined type POINT might have a decla