Example How to Show a SQL Query of entity Query in Drupal 8:
$query = \Drupal::entityQuery('node')
->condition('type', 'event')
->condition('field_location.entity:node.field_tag.entity:taxonomy_term', 'sailboat')
->__toString();
or try this:
$query = \Drupal::entityQuery('node')
->addTag('debug')
->execute();
Resulting in:
SELECT base_table.vid AS vid, base_table.nid AS nid
FROM
node base_table
INNER JOIN node_field_data node_field_data ON node_field_data.nid = base_table.nid
INNER JOIN node__field_location node__field_location ON node__field_location.entity_id = base_table.nid
LEFT OUTER JOIN node node ON node.nid = node__field_location.field_location_target_id
INNER JOIN node__field_venue_type node__field_venue_type ON node__field_venue_type.entity_id = node.nid
WHERE (node_field_data.type = 'event') AND (node__field_venue_type.field_venue_type_value = 'boat')
