Querying Resources by TV Value with xPDO in Evolution CMS

When you need more control than a frontend snippet provides, it is often easier to query Evolution CMS resources directly through xPDO. A common requirement is to fetch all resources whose template variable matches a specific value.

The original query pattern used an inner join against modTemplateVarResource:

$criteria = $modx->newQuery('modResource');
$criteria->innerJoin('modTemplateVarResource','TV', 'TV.contentid = modResource.id and TV.tmplvarid=20');
$criteria->where(array(
    'published' => 1,
    'deleted' => 0,
    'template' => 6,
    'TV.value' => ''
));

The useful part here is not just the join itself, but the mental model: TVs do not live on the resource row, so filtering by TV means joining the TV value table deliberately and targeting the exact TV ID you care about.

Once that is clear, you can count matching resources, fetch collections, sort them, or extend the condition set for more complex data-driven screens. It is a strong pattern for custom listings, dashboards, cleanup scripts, and migration utilities.