TV settings. Passing categories to select?

Question

MODX

Good day.
I'm trying to create a product catalog according to this manual https://modx.ru/novosti-i-stati/article/198/ .
When I create TV "Type of production". I select the output type Single selection and pass in possible values: @SELECT `pagetitle`, `alias` FROM ` modx_site_content` WHERE `parent`=`12` ORDER BY `pagetitle` .
When creating an element, the values ​​of the categories are not passed to the select

Answer 1

In some project, I used this construction for a list with a single choice. Do it by analogy, it should work.

@SELECT DISTINCT `value` FROM `site_tmplvar_contentvalues` WHERE `tmplvarid` = 6 ORDER BY `value` ASC