Anomaly regarding first entry in explain and explain join

Question

Hello there,
I have TPC-H benchmark database and I ran the following query with and without index on the column p_retailprice
select
     s_acctbal,s_name,n_name,p_partkey,p_mfgr,s_address,s_phone,s_comment
from
     dbo.part,dbo.supplier,dbo.partsupp,dbo.nation,dbo.region
where
     p_partkey = ps_partkey and p_retailprice <= 1.0
with index
first entry in Expalin is of  PART table , strategy is :range condition for index" and pagecount is 3627
first entry in explain join has table name PART and accumalated cost is 2
without index
both the explains have the value 17239 for pagecount and accumalated cost for the same entry
My question is what is the relation between first entry in both explains? The pagecount and accumalated costs(for the first entry)  for all queries when no index is applied comes to be the same but with index the value differs.

Answer 1

Hi again.
would you mind to show us the results of 'explain' and 'explain join'?
Be aware that in the normal 'explain'-output the "costs" that are printed in each line are not the assumed costs of that specific execution step.
Instead what you see there are the statistic information for the total object size (e.g. table or indexsize in pages).
regards,
Lars