adding field to database for product listing

Hello to all
I have added a field name 'product_ref' into the table 'product' and 'product_description'. The field is a reference number which references a part of the category image. I don't know to which table I should add that field. So I added that field to both the table, because I wanted to display the reference number in the product listing. I don't find the SQL statement which is used to fetch the data fields in the product listing. Any suggestion is appreciable
Thank you

Try includes/modules/product_listing.php

I have added
case 'PRODUCT_REF_NO':
$lc_text = TABLE_HEADING_REF; //TABLE_HEADING_REF="Ref No."
$lc_align = '';
$zc_col_count_description++;
break;
at line no. 29

case 'PRODUCT_REF_NO':
$lc_align= '';
$lc_text = $listing->fields['products_ref'];
break;
at line no. 100

But could not display the reference no. on product listing

Look to the tpl files for display...

the file you edited only makes the info available

I'm having a similar problem. (note: I am using the "Column Layout Grid for Product Listing" module.) I tried to reverse engineer the product listing but I couldn't figure out how to display my new field.

The "tpl_columnar_display.php" page appears to get all the content from the $list_box_contents array.

$list_box_contests array appears to get the field list from $column_list.

$column_list created from "includes/modules/pages/index/main_template_vars.php"

And finally, I added a "case" statement under the "switch ($column_list[$col])" in
"includes/modules/CUSTOM/product_listing.php"

I was able to hack my way through but I did it by modifying some of the core files and hardcoded some values. (Not the best way to run things.)

If someone has a cleaner process, please post your results!

Thank you in advance.