dumb dumb dumb

dumb dumb dumb

Post by California Dreamin' » Tue, 23 Apr 2002 10:17:55



Since this is an inner join:

[Table] +++++  [Table]

I thought an outer join must be like this:

++[Table]         [Table]++
+                                    +
++++++++++++++++++

Since that makes no sense, I've been confused for years.
Why use the terms "inner" and "outer" if they can't be taken literally?

 
 
 

dumb dumb dumb

Post by Keith Kratochvi » Tue, 23 Apr 2002 22:19:09


This information is copied directly from Books Online:

Subject: Using Outer Joins

"Using Outer Joins
Inner joins return rows only when there is at least one row from both tables
that matches the join condition. Inner joins eliminate the rows that do not
match with a row from the other table. Outer joins, however, return all rows
from at least one of the tables or views mentioned in the FROM clause, as
long as those rows meet any WHERE or HAVING search conditions. All rows are
retrieved from the left table referenced with a left outer join, and all
rows from the right table referenced in a right outer join. All rows from
both tables are returned in a full outer join"

I encourage you to read more information from Books Online.  You should be
able to access it from your SQL Server program group.

You can also download it from here:
http://www.microsoft.com/sql/techinfo/productdoc/2000/default.asp

--
Keith, SQL Server MVP


Quote:> Since this is an inner join:

> [Table] +++++  [Table]

> I thought an outer join must be like this:

> ++[Table]         [Table]++
> +                                    +
> ++++++++++++++++++

> Since that makes no sense, I've been confused for years.
> Why use the terms "inner" and "outer" if they can't be taken literally?


 
 
 

dumb dumb dumb

Post by Joe Celk » Wed, 24 Apr 2002 00:47:41


Quote:>> I've been confused for years. Why use the terms "inner" and "outer"

if they can't be taken literally? <<

Ever see a Venn diagram or Euler diagrams for sets?  Circles with colors
or X's in them for sets and their elements.  Draw two overlapping
circles.  The X's in the intersection are the inner join elements; the
X's in one of the circles are the preserved elements, and some of them
are outside the intersection.   Hope that graphic helps.

--CELKO--
 ===========================
 Please post DDL, so that people do not have to guess what the keys,
constraints, Declarative Referential Integrity, datatypes, etc. in your
schema are.

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dumb dumb dumb

Post by California Dreamin' » Wed, 24 Apr 2002 04:52:33


yes that helps


Quote:> >> I've been confused for years. Why use the terms "inner" and "outer"
> if they can't be taken literally? <<

> Ever see a Venn diagram or Euler diagrams for sets?  Circles with colors
> or X's in them for sets and their elements.  Draw two overlapping
> circles.  The X's in the intersection are the inner join elements; the
> X's in one of the circles are the preserved elements, and some of them
> are outside the intersection.   Hope that graphic helps.

> --CELKO--
>  ===========================
>  Please post DDL, so that people do not have to guess what the keys,
> constraints, Declarative Referential Integrity, datatypes, etc. in your
> schema are.

> *** Sent via Developersdex http://www.developersdex.com ***
> Don't just participate in USENET...get rewarded for it!

 
 
 

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