Mysql 批次号不会增加

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我试着查询名字的前三个字母 用于生成自动增量

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我尝试了这段代码，但输出错误。这里出了什么错

SET @ndx = 0;
SET @cur_hash = '';
SELECT id,Firstname ,CONCAT(left(Firstname ,3),IF(ndx>=0,CONCAT('--00',ndx),'')) BatchNumber
FROM (SELECT id,
   @new_hash := MD5(Firstname ),
   (@ndx := IF(@new_hash=@cur_hash,@ndx+1,1)) ndx,
   @cur_hash := MD5(Firstname ),
   Firstname
FROM (SELECT id,Firstname FROM sample ORDER BY Firstname ) AA) A order by id;

但我需要这种类型的输出：

    Firstname | Batchnumber
    ---------------------

    Anish     |  Ani001
    Anish     |  Ani001
    Uma       |  Uma001
    Anish     |  Ani001
    Uma       |  Uma001
    temp      |  tem001

当名称被多次插入时，我增加了批号。但它不起作用。

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我自己会努力找到答案，但这对我来说很难。有人能解决吗？

我没有发现你的问题。我没有发现你的问题。看见

    Firstname | Batchnumber
    ---------------------

    Anish     |  Ani001
    Anish     |  Ani001
    Uma       |  Uma001
    Anish     |  Ani001
    Uma       |  Uma001
    temp      |  tem001

    Firstname | Batchnumber
    -----------------------

       Anish     |  Ani001
       Anish     |  Ani002
       Uma       |  Uma001
       Anish     |  Ani003
       Uma       |  Uma002
       temp      |  tem001