Think\Db\Query::where PHP Method

    public function where($field, $op = null, $condition = null)
    {
        $param = func_get_args();
        array_shift($param);
        $this->parseWhereExp('AND', $field, $op, $condition, $param);
        return $this;
    }

 /**
  * 查询默认不包含软删除数据
  * @access protected
  * @param \think\db\Query $query 查询对象
  * @return void
  */
 protected function base($query)
 {
     $field = $this->getDeleteTimeField(true);
     $query->where($field, 'null');
 }