有没有办法从 MySQL 的列中提取与正则表达式匹配的文本? [英] Is there a way to extract text matching a regular expression from a column in MySQL?

问题描述

例如，如果特定列中的所有条目都具有 [az]+[0-9]+ 形式，那么如何仅提取前导字母，以便 asdf123 和 as3456 返回 'asdf' 和 'as'，分别?

For example, if all entries in a particular column have the form [a-z]+[0-9]+, how can one extract just the leading letters, so that asdf123 and as3456 return 'asdf' and 'as', respectively?

推荐答案

这在 mysql 正则表达式功能中是不可能的(除非安装一些似乎是为此设计的 udf).从技术上讲，由于 [0-9] 是一个有限集合，您可以在 LEAST 中抛出 10 个 LOCATE(注意 & invaliddate 0)，然后使用 SUBSTRING.不是一张漂亮的照片:

This is not posible with mysql regex capablities (unless installing some udf's which appear to be designed for that). Technically, as [0-9] is a limited set you could throw 10 LOCATE's in LEAST (watch out for & invalitdate 0), and use SUBSTRING. Not a pretty picture:

SET @var ='asjdasd35433';
SELECT SUBSTRING(@var,1,
  LEAST(
    IF(LOCATE(0,@var)=0,LENGTH(@var),LOCATE(0,@var)),
    IF(LOCATE(1,@var)=0,LENGTH(@var),LOCATE(1,@var)),
    IF(LOCATE(2,@var)=0,LENGTH(@var),LOCATE(2,@var)),
    IF(LOCATE(3,@var)=0,LENGTH(@var),LOCATE(3,@var)),
    IF(LOCATE(4,@var)=0,LENGTH(@var),LOCATE(4,@var)),
    IF(LOCATE(5,@var)=0,LENGTH(@var),LOCATE(5,@var)),
    IF(LOCATE(6,@var)=0,LENGTH(@var),LOCATE(6,@var)),
    IF(LOCATE(7,@var)=0,LENGTH(@var),LOCATE(7,@var)),
    IF(LOCATE(8,@var)=0,LENGTH(@var),LOCATE(8,@var)),
    IF(LOCATE(9,@var)=0,LENGTH(@var),LOCATE(9,@var))
   ) -1 ) as 'result';
+---------+
| result  |
+---------+
| asjdasd | 
+---------+

如果您需要，请查看 udf.否则，您最好获取该字段并在 MySQL 之外对其进行操作.

If you need it look at udf's. Otherwise you're just better of fetching the field and manipulate it outside MySQL.

如果数字适合整数，脏黑客可能会导致:

SET @var ='asjdasd35433';
SELECT SUBSTRING(@var,1,LENGTH(@var)-LENGTH(CAST(REVERSE(@var) as UNSIGNED)));
+---------+
| result  |
+---------+
| asjdasd |
+---------+

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