我如何使用正则表达式计算字符串中的单词

问题描述

我正在尝试在Oracle 10g中使用正则表达式对字符串中的单词进行计数。 我一直在尝试

select *
from books
where REGEXP_LIKE(title,'[ ]{2}'); 

，以便其返回的标题中至少包含3个单词。

解决方法

INSTR也是可行的选择。通过查找空格的第二次出现，将表明该字符串至少包含3个单词。

WITH
    books
    AS
        (SELECT 'Tom Sawyer' title FROM DUAL
         UNION ALL
         SELECT 'A tale of two cities' FROM DUAL
         UNION ALL
         SELECT 'The Little Prince' FROM DUAL
         UNION ALL
         SELECT 'Don Quixote' FROM DUAL)
SELECT title
  FROM books
 WHERE instr(title,' ',1,2) > 0;

如果您坚持使用正则表达式，则可以使用下面的正则表达式查找包含3个或更多单词的书。

WITH
    books
    AS
        (SELECT 'Tom Sawyer' title FROM DUAL
         UNION ALL
         SELECT 'A tale of two cities' FROM DUAL
         UNION ALL
         SELECT 'The Little Prince' FROM DUAL
         UNION ALL
         SELECT 'Don Quixote' FROM DUAL)
SELECT title
  FROM books
 WHERE REGEXP_LIKE (title,'(\S+\s){2,}');

（感谢@Littlefoot提供的书！）

,

REPLACE完成工作（经过一些计算）。

SQL> with books as
  2    (select 'Tom Sawyer' title      from dual union all
  3     select 'A tale of two cities'  from dual union all
  4     select 'The Little Prince'     from dual union all
  5     select 'Don Quixote'           from dual
  6    )
  7  select title
  8  from books
  9  where length(title) - length(replace(title,'')) >= 2;

TITLE
--------------------
A tale of two cities
The Little Prince

SQL>

,

以下内容简单易懂（适用于11g及更高版本）：

下面只是创建一些示例数据

>>> sample_set = { 2,2,8,3 }
>>> sample_set
{8,3}

以下是获取至少包含3个单词的标题的解决方案

create table books as
with tab as
(
    select 'Tom Sawyer' title from dual
    union all
    select 'A tale of two cities' from dual
    union all
    select 'The Little Prince' from dual
    union all
    select 'The_Little_Prince' from dual
    union all
    select 'Don Quixote' from dual
    union all
    select null from dual
)
select  title
from    tab;

输出：