1.14.4.1 Defining a UCA Collation Using LDML Syntax

To add a UCA collation for a Unicode character set without recompiling MySQL, use the following procedure. If you are unfamiliar with the LDML rules used to describe the collation's sort characteristics, see Section 1.14.4.2, “LDML Syntax Supported in MySQL”.

The example adds a collation named utf8mb4_phone_ci to the utf8mb4 character set. The collation is designed for a scenario involving a Web application for which users post their names and phone numbers. Phone numbers can be given in very different formats:

[phone]
[phone]
[phone]
[phone]
[phone]

The problem raised by dealing with these kinds of values is that the varying permissible formats make searching for a specific phone number very difficult. The solution is to define a new collation that reorders punctuation characters, making them ignorable.

1. Choose a collation ID, as shown in Section 1.14.2, “Choosing a Collation ID”. The following steps use an ID of 1029.

2. To modify the Index.xml configuration file. This file is located in the directory named by the character_sets_dir system variable. You can check the variable value as follows, although the path name might be different on your system:

   mysql> SHOW VARIABLES LIKE 'character_sets_dir';
   +--------------------+-----------------------------------------+
   | Variable_name      | Value                                   |
   +--------------------+-----------------------------------------+
   | character_sets_dir | /user/local/mysql/share/mysql/charsets/ |
   +--------------------+-----------------------------------------+

3. Choose a name for the collation and list it in the Index.xml file. In addition, you must provide the collation ordering rules. Find the <charset> element for the character set to which the collation is being added, and add a <collation> element that indicates the collation name and ID, to associate the name with the ID. Within the <collation> element, provide a <rules> element containing the ordering rules:

   <charset name="utf8mb4">
     ...
     <collation name="utf8mb4_phone_ci" id="1029">
       <rules>
         <reset>\u0000</reset>
         <i>\u0020</i> <!-- space -->
         <i>\u0028</i> <!-- left parenthesis -->
         <i>\u0029</i> <!-- right parenthesis -->
         <i>\u002B</i> <!-- plus -->
         <i>\u002D</i> <!-- hyphen -->
       </rules>
     </collation>
     ...
   </charset>

4. If you want a similar collation for other Unicode character sets, add other <collation> elements. For example, to define ucs2_phone_ci, add a <collation> element to the <charset name="ucs2"> element. Remember that each collation must have its own unique ID.

5. Restart the server and use this statement to verify that the collation is present:

   mysql> SHOW COLLATION WHERE Collation = 'utf8mb4_phone_ci';
   +------------------+---------+------+---------+----------+---------+
   | Collation        | Charset | Id   | Default | Compiled | Sortlen |
   +------------------+---------+------+---------+----------+---------+
   | utf8mb4_phone_ci | utf8mb4 | 1029 |         |          |       8 |
   +------------------+---------+------+---------+----------+---------+

Now test the collation to make sure that it has the desired properties.

Create a table containing some sample phone numbers using the new collation:

mysql> CREATE TABLE phonebook (
         name VARCHAR(64),
         phone VARCHAR(64) CHARACTER SET utf8mb4 COLLATE utf8mb4_phone_ci
       );
Query OK, 0 rows affected (0.09 sec)
mysql> INSERT INTO phonebook VALUES ('Svoj','[phone]');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO phonebook VALUES ('Hf','[phone]');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO phonebook VALUES ('Bar','[phone]');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO phonebook VALUES ('Ramil','(7912) 800 80 03');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO phonebook VALUES ('Sanja','[phone]');
Query OK, 1 row affected (0.00 sec)

Run some queries to see whether the ignored punctuation characters are in fact ignored for comparison and sorting:

mysql> SELECT * FROM phonebook ORDER BY phone;
+-------+--------------------+
| name  | phone              |
+-------+--------------------+
| Sanja | [phone] |
| Bar   | [phone]   |
| Svoj  | [phone]   |
| Ramil | (7912) 800 80 03   |
| Hf    | [phone] |
+-------+--------------------+
5 rows in set (0.00 sec)
mysql> SELECT * FROM phonebook WHERE phone='[phone]';
+------+------------------+
| name | phone            |
+------+------------------+
| Bar  | [phone] |
+------+------------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM phonebook WHERE phone='79128008001';
+------+------------------+
| name | phone            |
+------+------------------+
| Bar  | [phone] |
+------+------------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM phonebook WHERE phone='7 9 1 2 8 0 0 8 0 0 1';
+------+------------------+
| name | phone            |
+------+------------------+
| Bar  | [phone] |
+------+------------------+
1 row in set (0.00 sec)