Locate text position, extract text and insert in new column in MySQL

Question

I have the following example of rows in a MySQl table

              Column A    

Row1    Lauguage=English&Country=USA&Gender=Male
Row2    Gender=Female&Language=French&Country=
Row3    Country=Canada&Gender=&Language=English

How can I achieve the following: For example, I need to look for Country

1. I need to locate the position of Country in this text column. This changes from row to row.
2. I need to then ignore the parameter 'Country=' and only extract the value. In some cases this will be NULL (like example in Row2) while in some rows I need the values followed by '=' (like example in Row1 & Row3). But, I need to make sure I get the value only. Not the next parameter separated by '&'
3. Once I have extracted the values of the Country parameter, I need to create a new column where these values will now be extracted and stored.

End Result: New Column

              Column B                                                

Row1            USA                            
Row2                              
Row3           Canada                                  

Any help here would be appreciated! Thanks!

Answer 1

You can pick the text following the 'Country=', and then once you have that substring, pick the text before the first '&'

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(ColumnA, 'Country=', -1), '&', 1) AS ColumnB
FROM `atable`

See http://dev.mysql.com/doc/refman/5.6/en/string-functions.html#function_substring-index

---

Here's a test to demonstrate:

mysql> SELECT * FROM atable;
+------+------------------------------------------+
| row  | columna                                  |
+------+------------------------------------------+
| Row1 | Lauguage=English&Country=USA&Gender=Male |
| Row2 | Gender=Female&Language=French&Country=   |
| Row3 | Country=Canada&Gender=&Language=English  |
+------+------------------------------------------+

mysql> SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(ColumnA, 'Country=', -1), '&', 1) AS ColumnB FROM atable;
+---------+
| ColumnB |
+---------+
| USA     |
|         |
| Canada  |
+---------+

---

Re your followup question:

INSERT INTO atable VALUES ('Row4', 'Gender=&Language=English');

SELECT `row`, IF(LOCATE('Country=', ColumnA)>0, 
  COALESCE(
    NULLIF(SUBSTRING_INDEX(SUBSTRING_INDEX(ColumnA, 'Country=', -1), '&', 1), ''), 
    'Blank string is not valid!'), 
 'Missing Country!') AS ColumnB     
FROM `atable`

+------+----------------------------+
| row  | ColumnB                    |
+------+----------------------------+
| Row1 | USA                        |
| Row2 | Blank string is not valid! |
| Row3 | Canada                     |
| Row4 | Missing Country!           |
+------+----------------------------+