RE: SQL vs. traditional I/O?

[Vern Hamberg <vhamberg@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Joel

This is confusing:

At 09:17 AM 7/23/2004, you wrote:

-snip-

> And for clarity, a View incorporates an index.  A view has columnar
> abilities that are not available in DDS.  A view is more than an index,
> where as a logical file, no matter how complex, is just an index.  A
> view is limited to the subfields mentioned within.

-snip-

AFAIK, an SQL view is definitely NOT an SQL index - these are both LFs with 
special properties that are different from those of the traditional LFs.

And old-style LFs combine, IIRC, some of the qualities of both views and 
indexes. I.e., an LF can be defined with a subset of the fields in its 
parent PF. You don't have to define it with all the fields. That was always 
the point about column-level visibility, where you could hide things by 
giving users access (through apps, we hope) to a logical instead of the 
underlying physical.

And the K-specs are the index definition.

And what is a view, after all? Look at DSPFD of a view - what you see in it 
is an SQL statement. I do not believe that a view is a logical file in the 
old sense - it is not an access path maintained by the system. In fact, it 
is a dynamic SQL statement, executed afresh each time the view is accessed. 
I could easily be wrong about the specifics here, but I think I am close.

An SQL index, it seems, is closer to a keyed logical file, but it does not 
have subsetting of the column set. It only has a binary tree structure for 
the key fields.

Am I close?

Vern