如何从MySQL的文本字段中提取两个连续的数字? [英] How to extract two consecutive digits from a text field in MySQL?

问题描述

我有一个MySQL数据库，查询如下:

I have a MySQL database and I have a query as:

SELECT `id`, `originaltext` FROM `source` WHERE `originaltext` regexp '[0-9][0-9]'

这将检测所有带有2位数字的原始文本.

This detects all originaltexts which have numbers with 2 digits in it.

我需要MySQL将这些数字作为字段返回，以便我可以进一步处理它们.

I need MySQL to return those numbers as a field, so i can manipulate them further.

理想情况下，如果我可以添加应该大于20的其他条件，那很好，但我也可以单独进行.

Ideally, if I can add additional criteria that is should be > 20 would be great, but i can do that separately as well.

推荐答案

如果您想在数据库中拥有更多的正则表达式功能，可以考虑使用

If you want more regular expression power in your database, you can consider using LIB_MYSQLUDF_PREG. This is an open source library of MySQL user functions that imports the PCRE library. LIB_MYSQLUDF_PREG is delivered in source code form only. To use it, you'll need to be able to compile it and install it into your MySQL server. Installing this library does not change MySQL's built-in regex support in any way. It merely makes the following additional functions available:

PREG_CAPTURE 从字符串中提取正则表达式匹配项. PREG_POSITION返回正则表达式与字符串匹配的位置. PREG_REPLACE对字符串执行搜索和替换. PREG_RLIKE测试正则表达式是否与字符串匹配.

PREG_CAPTURE extracts a regex match from a string. PREG_POSITION returns the position at which a regular expression matches a string. PREG_REPLACE performs a search-and-replace on a string. PREG_RLIKE tests whether a regex matches a string.

所有这些函数均使用正则表达式作为其第一个参数.此正则表达式的格式必须类似于Perl正则表达式运算符.例如.要测试正则表达式是否与主题区分大小写，请使用MySQL代码PREG_RLIKE('/regex/i'，subject).这类似于PHP的preg函数，后者对于PHP字符串内的正则表达式也需要//分隔符.

All these functions take a regular expression as their first parameter. This regular expression must be formatted like a Perl regular expression operator. E.g. to test if regex matches the subject case insensitively, you'd use the MySQL code PREG_RLIKE('/regex/i', subject). This is similar to PHP's preg functions, which also require the extra // delimiters for regular expressions inside the PHP string.

如果您想更简单一些，可以更改此功能以更好地满足您的需求.

If you want something more simpler, you could alter this function to suit better your needs.

CREATE FUNCTION REGEXP_EXTRACT(string TEXT, exp TEXT)
-- Extract the first longest string that matches the regular expression
-- If the string is 'ABCD', check all strings and see what matches: 'ABCD', 'ABC', 'AB', 'A', 'BCD', 'BC', 'B', 'CD', 'C', 'D'
-- It's not smart enough to handle things like (A)|(BCD) correctly in that it will return the whole string, not just the matching token.

RETURNS TEXT
DETERMINISTIC
BEGIN
  DECLARE s INT DEFAULT 1;
  DECLARE e INT;
  DECLARE adjustStart TINYINT DEFAULT 1;
  DECLARE adjustEnd TINYINT DEFAULT 1;

  -- Because REGEXP matches anywhere in the string, and we only want the part that matches, adjust the expression to add '^' and '$'
  -- Of course, if those are already there, don't add them, but change the method of extraction accordingly.

  IF LEFT(exp, 1) = '^' THEN 
    SET adjustStart = 0;
  ELSE
    SET exp = CONCAT('^', exp);
  END IF;

  IF RIGHT(exp, 1) = '$' THEN
    SET adjustEnd = 0;
  ELSE
    SET exp = CONCAT(exp, '$');
  END IF;

  -- Loop through the string, moving the end pointer back towards the start pointer, then advance the start pointer and repeat
  -- Bail out of the loops early if the original expression started with '^' or ended with '$', since that means the pointers can't move
  WHILE (s <= LENGTH(string)) DO
    SET e = LENGTH(string);
    WHILE (e >= s) DO
      IF SUBSTRING(string, s, e) REGEXP exp THEN
        RETURN SUBSTRING(string, s, e);
      END IF;
      IF adjustEnd THEN
        SET e = e - 1;
      ELSE
        SET e = s - 1; -- ugh, such a hack to end it early
      END IF;
    END WHILE;
    IF adjustStart THEN
      SET s = s + 1;
    ELSE
      SET s = LENGTH(string) + 1; -- ugh, such a hack to end it early
    END IF;
  END WHILE;

  RETURN NULL;

END

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