RE: SQL Existence Check

["Walden H. Leverich" <WaldenL@xxxxxxxxxxxxxxx>]

>From: Vernon Hamberg [mailto:vhamberg@attbi.com]
>The other factor here is that SETLL will have less IO than CHAIN

That was my understanding too, however I could never reconcile that with my
understanding of the Binary Radix Tree. Doesn't a B* tree store only enough
of the key to identify which page of the table the row is on? If so I can
get a negative hit from the index itself, but I must go to the table to get
a positive hit, no?

Given a table with Name a key and the following rows:

Walden
Mike
Walter
Bill

Wouldn't I have three top level index pages, one for W, one for B and one
for M pointing to three pages in the table. If so, I know from the index
that "George" is not on the table, but I need to look at the table to find
out if "William" is a valid row.

Where is my understanding of B* broken?

-Walden
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Walden H Leverich III
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