invalid joins

[mjsoule]

In An Introduction to SQL and PL/SQL, Oracle, lesson 4 there is a discussion of Cartesian products. The following statement is in the slides.

Cartesian Product
A Cartesian product is generated if a join condition is omitted OR a join condition is invalid.

What is an example of an invalid join?

 

[MalcolmW]

A common invalid join is when you are doing up a shirt, and the buttons and the button holes end up not matching.
Another one is
Where 1 <> 0
Another one (in current syntax)
SELECT *
FROM Table1 INNER JOIN Table2 ON 1 <> 0

Usually Cartesian products are generated in error, but not always.

Malcolm
wynden@telus.net
November is &quot;be kind to dogs and programmers&quot; month. Or is that &quot;dogs or programmers&quot;?

 

[mjsoule]

Had not heard this one
A common invalid join is when you are doing up a shirt, and the buttons and the button holes end up not matching.

Use this already
Another one is
Where 1 <> 0
Another one (in current syntax)
SELECT *
FROM Table1 INNER JOIN Table2 ON 1 <> 0

Did not know Cartesian products are not always created.

Usually Cartesian products are generated in error, but not always.