core/DB.php
public static function dropField(string $tbname, string $field)
    {
        return self::engine()->dropField($tbname, $field);
    }
public static function dropField(string $tbname, string $field)
    {
        return self::engine()->dropField($tbname, $field);
    }
删除字段
@param string $tbname
@param string $field
@return int|null
@throws MysqlException