protected function createFallbackQuery($category, $language, $fallbackLanguage)
{
return (new Query())->select(['message' => 't1.message', 'translation' => 't2.translation'])->from(['t1' => $this->sourceMessageTable, 't2' => $this->messageTable])->where(['t1.id' => new Expression('[[t2.id]]'), 't1.category' => $category, 't2.language' => $fallbackLanguage])->andWhere(['NOT IN', 't2.id', (new Query())->select('[[id]]')->from($this->messageTable)->where(['language' => $language])]);
}