Table Index

Hi,

I need to understand something. I'm trying to improve performance on a report. The most selections do not use table keys to acess, so, somebody create some indexes with the idea to make the selection faster. Here is one example:

SELECT *

FROM coep

INTO TABLE t_coep

WHERE bukrs IN s_bukrs

AND gjahr = p_gjahr

AND perio IN r_perio

AND kstar IN s_kstar.

The table COEP has a index with fields bukrs, gjahr, perio e kstar. But, after use ST22 I discover that the database is not using this index. Its use the "normal one".

I know that is not a good programming pratice use select * (I will take out and put only the fields that I want).

Well, somebody com explain to me how the indexes works or have some document about it.

I appreciate any kind of help.