/**
  * {@inheritdoc}
  */
 public function whereToSql($col, $sign, $expression)
 {
     if ($col === 'UNIX_TIMESTAMP(sch.comment_time)') {
         return 'sch.comment_time ' . $sign . ' ' . $this->timestampForSql($this->valueToTimestamp($expression));
     } else {
         return parent::whereToSql($col, $sign, $expression);
     }
 }
 /**
  * {@inheritdoc}
  */
 public function whereToSql($col, $sign, $expression)
 {
     if ($col === 'UNIX_TIMESTAMP(sh.state_time)') {
         return 'sh.state_time ' . $sign . ' ' . $this->timestampForSql($this->valueToTimestamp($expression));
     } elseif ($col === $this->columnMap['history']['type'] && !is_array($expression) && array_key_exists($expression, $this->types)) {
         return 'sh.state_type ' . $sign . ' ' . $this->types[$expression];
     } else {
         return parent::whereToSql($col, $sign, $expression);
     }
 }