某库表的字段是字符串。

现在要找出至少含有 5 个连续按字母表排序的字母的字符串，或者说，连续升序排列的子串中，最长的子串的长度大于等于 5 的字符串。注意，排除掉非字母的字符。

SQL：

SELECT value
FROM   table_name t
       CROSS JOIN LATERAL (
         SELECT MIN(lvl) AS start_pos
         FROM   (
           SELECT LEVEL AS lvl,
                  SUBSTR(t.value, LEVEL, 1) AS ch
           FROM   DUAL
           CONNECT BY LEVEL <= LENGTH(t.value)
         )
         MATCH_RECOGNIZE(
           ORDER BY lvl
           MEASURES
             FIRST(lvl) AS lvl
           PATTERN (first_row consecutive{3,})
           DEFINE first_row   AS (ch BETWEEN 'A' AND 'Z' OR ch BETWEEN 'a' AND 'z'),
                  consecutive AS (ch BETWEEN 'A' AND 'Z' OR ch BETWEEN 'a' AND 'z')
                                 AND ASCII(PREV(ch)) + 1 = ASCII(ch)
         )
         HAVING MIN(lvl) > 0
       )

SQL要用嵌套子查询 +CONNECT BY 模拟序列，再用 MATCH_RECOGNIZE 处理序列，代码繁琐难懂。SPL 直接提供了序列计算函数：https://try.esproc.com/splx?4yy

A1：加载数据。

A2：将字符串按字符拆成序列，对序列分组，当当前成员小于等于上一个成员或者上个成员非字母时，开始新的分组，选出最长的组的长度大于等于 5 的字符串。函数 group 在分组后可以保持分组子集用于后续处理，而不是立即计算，@i 表示按条件分组。

问题来源：https://stackoverflow.com/questions/78151968/find-consecutive-alphabetical-characters-in-string