This document discusses self joins in Microsoft Access. A self join joins a table to itself to show hierarchical relationships like parts lists or employee managers. The presentation shows how to create a query that lists employees along with their managers by joining the Employees table to itself. It demonstrates adding the Employees table twice to the query designer, giving one an alias of "Managers", and creating an outer join between the tables on the EmpNo and MgrNo fields to return results even if an employee has no manager. The results of the sample query on the provided Employees table are shown.

1. Orange Coast Database Associates
Laguna Niguel, CA 92677
Slides.1@dhdursoassociates.com
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Self Joins
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2. 

A self join joins a table to itself
This is useful for hierarchical relationships
 Parts lists
 Employee relationships (manager/supervisor)
 Customer referrals
 Etc.

This presentation shows how to create a
query in Microsoft Access that joins a table to
itself
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3. 
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MgrNo is a foreign key in the employees table that refers to the table’s
own primary key, EmpNo.
We will create a query that lists each employee along with their
manager’s name.
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4. 

This database is available on Box.com.
The presentation is on Slideshare.
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5. 
Below is a screenshot of the sample
Employees table
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6. 
Add the Employees table to the query designer twice. The
second time Access will give it the name Employees_1.
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7. 
Right click on the title of the 2nd Employees table
and give it an alias of Managers.
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8. 

Create an outer join relationship between the two tables. This will show the employee even if
they have no supervisor in the employees table (say the President).
Populate the fields to be shown.
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9. 
Save the query and run it. Below are the
results from our sample table.
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10. 

If desired the relationship of a table joined to
itself can be created as a permanent link
using the relationship designer.
The example we used in this presentation is a
one-to-many relationship (one employee
reports to one manager, one manager may
have several employees). Many to many
relationships such as for matrix management
are also possible by using a 3rd intersection
table.
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11. 

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This presentation showed how to create a
simple self join query in Access.
You should find many uses for this: reporting
relationships, parts lists, customer
referrals, etc.
Go to Slideshare to find related Microsoft
Access presentations.
[end self joins]
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