使用正则表达式将一列拆分为多列

Question

I have a table and some data:

-- Table
CREATE TABLE IF NOT EXISTS `myTable` (
  `myColumn` varchar(32) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- Data
INSERT INTO `myTable` (`myColumn`) VALUES
('AAA BBB CCC'),
('AA BB CCCC'),
('BBB CC AAAA'),
('C AAA BBB'),
('CCC AA BBB');

I would like to run a SELECT query that return 3 columns.

The columns should be called A , B , and C .

The result should look something like:

+------+-----+------+
| A    | B   | C    |
+------+-----+------+
| AAA  | BBB | CCC  |
| AA   | BB  | CCCC |
| AAAA | BBB | CC   |
| AAA  | BBB | C    |
| AA   | BBB | CCC  |
+------+-----+------+

I have three regular expressions which, by using them all, can match all data:

^([A]+) ([B]+) ([C]+)$
^([B]+) ([C]+) ([A]+)$
^([C]+) ([A]+) ([B]+)$

Is it possible to use these regular expressions to produce such a result?

If so, would appreciate an example, even if only for a subset of the problem.

Answer 1

This can't be done using regexes in MySQL. Unfortunately, MySQL support regexes only as a boolean condition (notably in where clauses), but not to extract nor alter the content of a string.

You may however achieve what you described entirely from a MySQL query, using substring_index . Here is an example usage for your scenario.

SELECT substring_index(substring_index(myColumn, ' ', 1), ' ', -1) AS `A`, 
       substring_index(substring_index(myColumn, ' ', 2), ' ', -1) AS `B`,
       substring_index(                myColumn         , ' ', -1) AS `C`
  FROM ...  

Alternatively, if you must absolutely use regexes, then you might pipe MySQL's output to some regex engine. Ask me if you need more info about this strategy.