MySQL如何给查询结果添加行号

SET @rownum:=0; -- 注意：“：=”表示赋值，“=”表示比较，“@”表示变量
 
SELECT provinces.*,@rownum:=@rownum+1 as rownum 
FROM provinces;

SELECT provinces.*,@rownum:=@rownum+1 as rownum
FROM provinces,(SELECT @rownum:=0) a;

 
-- MySQL8.0以上版本支持函数,和oracle数据库语法一样
SELECT provinces.*,row_number() over(ORDER BY id) as rownum
FROM provinces;

CREATE TABLE `my_tb` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `parent_code` varchar(255) DEFAULT NULL,
  `code` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;

INSERT INTO `my_tb` (  `parent_code`, `code`) VALUES ('01', '001');
INSERT INTO `my_tb` (  `parent_code`, `code`) VALUES ('01', '002');
INSERT INTO `my_tb` (  `parent_code`, `code`) VALUES ('02', '001');
INSERT INTO `my_tb` (  `parent_code`, `code`) VALUES ('01', '003');
INSERT INTO `my_tb` (  `parent_code`, `code`) VALUES ('02', '002');
INSERT INTO `my_tb` (  `parent_code`, `code`) VALUES ('03', '001');
INSERT INTO `my_tb` (  `parent_code`, `code`) VALUES ('04', '001');

-- 生成 行号
select @r:=@r+1 as row_num , a.* from  my_tb a ,(select @r:=0) b

-- 生成 分组排序号

select  
     @group_row:=CASE when @parent_code=a.parent_code then  @group_row+1 else 1 end as groupRow,
     @parent_code:=a.parent_code as parent_code,
     a.code  

  from  my_tb a ,( select @group_row:=1, @parent_code:='') as b
 ORDER BY   a.parent_code , a.code