Mysql SQL查找下一个可用字符串键

我需要在具有字符串键的表上查找下一个可用ID。我的例子如下：

菜品表（第一列）

SQL:

输出：

DSH0000000006

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如果我删除了#5，那么它会返回#5，但不会返回“DSH0000000001”。

您应该添加对起始值的测试。使用当前方法，只能获得大于表中存在的最小值的值

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您可以使用IF（）来区分这两种可能性。

您可以使用变量来构建连续的id，然后比较第一个不匹配的id：

SELECT
  CONCAT('DSH', LPAD(seq, 10, '0')) AS k
FROM
  (SELECT
    @seq:=@seq+1 AS seq,
    num
  FROM
    (SELECT
       CAST(SUBSTR(table_id, 4) AS UNSIGNED) AS num
     FROM
       t
     UNION ALL
     SELECT
        MAX(CAST(SUBSTR(table_id, 4) AS UNSIGNED))+2 AS num
     FROM 
       t
     ORDER BY
       num) AS ids
   CROSS JOIN 
      (SELECT @seq:=0) AS init 
  ) AS pairs
WHERE
  seq!=num
LIMIT 1

---

Fiddle可用。

Hi-VMai，感谢您的回复，但您如何在查询中检查起始值？谢谢，如果ID列表（即最高ID号）中没有空白，那么您的查询似乎不会返回下一个ID。请参见此处的SQLFiddle（）。“恐怕你的SQL超出了我的知识范围。”我注意到了这一点。几乎不需要修理。我已经更新了Hanks Alma Do！真棒的帮助！

DSH0000000006

SELECT
  CONCAT('DSH', LPAD(seq, 10, '0')) AS k
FROM
  (SELECT
    @seq:=@seq+1 AS seq,
    num
  FROM
    (SELECT
       CAST(SUBSTR(table_id, 4) AS UNSIGNED) AS num
     FROM
       t
     UNION ALL
     SELECT
        MAX(CAST(SUBSTR(table_id, 4) AS UNSIGNED))+2 AS num
     FROM 
       t
     ORDER BY
       num) AS ids
   CROSS JOIN 
      (SELECT @seq:=0) AS init 
  ) AS pairs
WHERE
  seq!=num
LIMIT 1