Hi gurus informix,

I doing a select in table xxxxx, the field in the where clause is unique index, I am executing set explain and the cost is this.

Estimated Cost: 7668

The table have 3130165 rows.

How can low the Estimated Cost.

Thank you for you help.

1) what ids version?
2) copy here all result of set explain and select statment...

if you want to know how make optimization in SQL my suggestion is:
- manual IBM Informix Performance Guide
- slides of IIUG conferences ( www.iiug.org )


here you have links to manual, tutorial, etc..
http://www-1.ibm.com/support/docview...id=swg21250290

The version is 9.40 UC7

QUERY:
------
select {+explain avoid_execute} first 1 totgn_rdtotgne_c, totgn_feulttot_k from informix.prtotgne
where totgn_rdcodope_k = 3
and totgn_feulttot_k <= '2007-09-20'
and totgn_rdtipgar_p = 2
and totgn_rdclvope_k = 9999
and totgn_rdmodal_p = 4115
and totgn_rdsubmod_p = 9999
and totgn_rdcodpro_p = 99
and totgn_rdrngimp_k = 99
order by totgn_feulttot_k desc

DIRECTIVES FOLLOWED:
EXPLAIN
AVOID_EXECUTE
DIRECTIVES NOT FOLLOWED:

Estimated Cost: 10629
Estimated # of Rows Returned: 1

1) informix.prtotgne: INDEX PATH

(1) Index Keys: totgn_rdcodope_k totgn_feulttot_k totgn_rdtipgar_p totgn_rdclvope_k totgn_rdmodal_p totgn_rdsubmod_p totgn
_rdcodpro_p totgn_rdrngimp_k (Key-First) (Serial, fragments: ALL)
Lower Index Filter: (informix.prtotgne.totgn_rdcodope_k = 3 AND informix.prtotgne.totgn_feulttot_k <= 20070920 )
Key-First Filters: (informix.prtotgne.totgn_rdcodpro_p = 99 ) AND
(informix.prtotgne.totgn_rdmodal_p = 4115 ) AND
(informix.prtotgne.totgn_rdrngimp_k = 99 ) AND
(informix.prtotgne.totgn_rdsubmod_p = 9999 ) AND
(informix.prtotgne.totgn_rdclvope_k = 9999 ) AND
(informix.prtotgne.totgn_rdtipgar_p = 2 )

Thank you for you help.