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
LONG and LONG RAW You use the LONG datatype to store the variable-length character strings. The LONG datatype is such as the VARCHAR2 datatype, except that the maximum length o

Using the Collection Methods The collection methods below help to generalize the code and make collections easier to use and also make your applications easier to maintain:

Using EXCEPTION_INIT To handle unnamed internal exceptions, you should use the OTHERS handler or the pragma EXCEPTION_INIT. The pragma is a compiler directive that can be th

Bitmap Join Indexes - This feature will increase the performance and detains the size and format of your databases in data Character Semantics and Globalization -This featur

Grouping and Ungrouping in SQL Example specifying EXAM_MARK in place of COURSE in the main FROM clause. Example: Obtaining C_ER2 from EXAM_MARK SELECT CourseId, CAST

Package Body: The package specification is implemented by the package body. That is, the package body has the definition of every cursor and the subprogram declared in the pac

Example of COALESCE operator Example: Give the total of marks for each exam (simplified solution) SELECT CourseId, COALESCE ((SELECT SUM (Mark) FROM EXAM_MARK AS EM

"Not Enforced" Table Constraints A constraint that is not enforced is not really a constraint within the meaning of the act, but SQL does have such a concept and it needs to b

%NOTFOUND The %NOTFOUND is the logical opposite of the %FOUND. The %NOTFOUND yields TRUE when an INSERT, UPDATE, or DELETE statement affected no rows, or the SELECT INTO state

EXECUTE Privilege To call an invoker-rights routine straightforwardly, the users should have the EXECUTE privilege on that routine. By yielding the privilege, you permit a user