如何检查MySQL中以前的记录？

我要分类的序列号。这意味着产出将减少

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有人能帮忙吗？

一个非常好的解决方案是使用用户定义的变量，例如

+----+--------+----------+--------+
| ID |  Name  | Category | Count  |
+----+--------+----------+--------+
|  1 | Cat    | Animal   |      1 |
|  2 | Loin   | Animal   |      2 |
|  3 | Dog    | Animal   |      3 |
|  4 | Red    | Color    |      1 |
|  5 | Hen    | Bird     |      1 |
|  6 | Parrot | Bird     |      2 |
+----+--------+----------+--------+

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基本上，您需要（分区）上的行数的等价物，您可以使用自连接和聚合：

select
id,
name,
category,
rn as `count`
from (
  select
  id,name,category,
  @rn:= if(category = @prev_category,@rn+1,1) as rn,
  @prev_category:= category
  from my_table,(select @rn:=1,@prev_category:= null)x
  order by category,id
)x

输出：

SELECT a.id, a.name, a.category, count(*) AS `Count`
FROM tab a
JOIN tab b 
  ON a.Category= b.Category AND a.ID >= b.ID
GROUP BY a.id, a.name, a.category;

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我在查询检查中尝试使用上一个变量@s:=0，但问题出现在两个以上的名称中。

SELECT a.id, a.name, a.category, count(*) AS `Count`
FROM tab a
JOIN tab b 
  ON a.Category= b.Category AND a.ID >= b.ID
GROUP BY a.id, a.name, a.category;

╔════╦════════╦══════════╦═══════╗
║ ID ║  Name  ║ Category ║ Count ║
╠════╬════════╬══════════╬═══════╣
║  1 ║ Cat    ║ Animal   ║     1 ║
║  2 ║ Loin   ║ Animal   ║     2 ║
║  3 ║ Dog    ║ Animal   ║     3 ║
║  4 ║ Red    ║ Color    ║     1 ║
║  5 ║ Hen    ║ Bird     ║     1 ║
║  6 ║ Parrot ║ Bird     ║     2 ║
╚════╩════════╩══════════╩═══════╝