core/SqlSelector.php
public function field(string $field, $args = null)
    {
        $this->fieldItem = new SqlItem($field, $args);
        return $this;
    }
public function field(string $field, $args = null)
    {
        $this->fieldItem = new SqlItem($field, $args);
        return $this;
    }
设置查询字段
@param string $field
@param null $args
@return $this