Simple select very slow when used into a match code field

[Giovanni Chiozza]

Hello all,

I got a table with about 21.000 records about articles master data
The table's fields are few : article_id, codart, codart2, descrizione, um
INDEXes PRIMARY --> article_id, index_codart --> codart index_decri --> descrizione

The select used on a lookup field is the following:

SELECT article_id, concat(codart, " - ", descrizione) as descri_item
FROM articles
ORDER BY descri_item

How can I speed up this select in order to have a prompt show of records ?
Now I have to wait about 3/4 seconds that for a quick data entry is really to much.

Many thanks
Giò