Re: SQL record exists -- MIDRANGE-L

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Hi Rob

This is the case. It used to be called the index-only access method. I think now it is known as radix index probe. The OP might want to learn more about SQL access methods in the Database Performance and Query Optimization manual - the 6.1 version is at

http://publib.boulder.ibm.com/infocenter/iseries/v6r1m0/topic/rzajq/rzajq.pdf

To quote from that manual -

"If all of the columns necessary to satisfy the query request for a table can be found as keys of an index, then the Table Probe is not required and the query uses Index Only Access."

Regards
Vern

rob@xxxxxxxxx wrote:

Thomas,

If one has an index built over the customer number, and the only thing read is the customer number then the entire table is not read, just the index. For example, if I do this
select count(*), itemclass
from itemmaster
group by itemclass

and there is an index over the itemclass then the engine reads only the index and doesn't touch the physical file.

I believe that is true for a Primary or unique index built into the table as well.

Rob Berendt

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