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== Character Sets and Collations in MySQL==

MySQL supports the use of character sets for the MyISAM, MEMORY, NDBCluster, and InnoDB storage engines.
A character set is a set of symbols and encodings.
A collation is a set of rules for comparing characters in a character set.
The MySQL server can support multiple character sets.
To list the available character sets, use the SHOW CHARACTER SET statement
Quote from MySQL document http://www.mysql.ru



<source lang="sql">
mysql>
mysql> SHOW CHARACTER SET;
+----------+-----------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
+----------+-----------------------------+---------------------+--------+
36 rows in set (0.00 sec)
mysql></source>

== character_set_system==



<source lang="sql">
SHOW VARIABLES LIKE "character_set_system";
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| character_set_system | utf8 |
+----------------------+-------+
1 row in set (0.00 sec)
mysql></source>

== Column Character Set and Collation==

Every CHAR, VARCHAR, or TEXT Column has a column character set and a column collation.
Column definition syntax has optional clauses for specifying the column character set and collation:



<source lang="sql">
col_name {CHAR | VARCHAR | TEXT} (col_length)[CHARACTER SET charset_name] [COLLATE collation_name]</source>

== Database, Table, and Column Definition with Character and collate==



<source lang="sql">
mysql>
mysql> CREATE DATABASE myDatabase DEFAULT CHARACTER SET latin2 COLLATE latin2_czech_ci;
Query OK, 1 row affected (0.02 sec)
mysql>
mysql>
mysql>
mysql> USE myDatabase;
Database changed
mysql>
mysql> CREATE TABLE myTable
-> (
-> c1 CHAR(10)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> drop database myDatabase;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> use test;
Database changed</source>

== Every database has a database character set and a database collation.==

The CREATE DATABASE and ALTER DATABASE statements have optional clauses for specifying the database character set and collation:
All database options are stored in a text file named db.opt that can be found in the database directory.



<source lang="sql">
CREATE DATABASE db_name
[[DEFAULT] CHARACTER SET charset_name]
[[DEFAULT] COLLATE collation_name]
ALTER DATABASE db_name
[[DEFAULT] CHARACTER SET charset_name]
[[DEFAULT] COLLATE collation_name]</source>

== List the available character set==



<source lang="sql">
SHOW CHARACTER SET;
+----------+-----------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
+----------+-----------------------------+---------------------+--------+
36 rows in set (0.00 sec)
mysql></source>

== Server Character Set and Collation==

You can use --character-set-server for the character set.
Along with it, you can add --collation-server for the collation.



<source lang="sql">
shell> mysqld
shell> mysqld --character-set-server=latin1
shell> mysqld --character-set-server=latin1 --collation-server=latin1_swedish_ci</source>

== SHOW CREATE DATABASE displays the CREATE DATABASE statement that creates a given database:==



<source lang="sql">
mysql>
mysql> SHOW CREATE DATABASE test;
+----------+-----------------------------------------------------------------+
| Database | Create Database |
+----------+-----------------------------------------------------------------+
| test | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-----------------------------------------------------------------+
1 row in set (0.00 sec)
mysql></source>

== SHOW CREATE TABLE displays the CREATE TABLE statement to create a given table.==



<source lang="sql">
mysql>
mysql> CREATE TABLE myTable
-> (
-> c1 CHAR(10)
-> ) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql> desc myTable;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| c1 | char(10) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
1 row in set (0.00 sec)
mysql>
mysql> SHOW CREATE TABLE myTable;
+---------+------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+---------+------------------------------------------------------------------------------------------------------------------------------------------------+
| myTable | CREATE TABLE `mytable` (
`c1` char(10) collate latin1_danish_ci default NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_danish_ci |
+---------+------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql></source>

== Table and Column Definition with character and collate==



<source lang="sql">
mysql>
mysql> CREATE TABLE myTable
-> (
-> c1 CHAR(10)
-> ) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> desc myTable;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| c1 | char(10) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
1 row in set (0.00 sec)
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql></source>

== Table Character Set and Collation==

Every table has a table character set and a table collation.
The CREATE TABLE and ALTER TABLE statements have optional clauses for specifying them:



<source lang="sql">
CREATE TABLE tbl_name (column_list)
[[DEFAULT] CHARACTER SET charset_name] [COLLATE collation_name]]
ALTER TABLE tbl_name
[[DEFAULT] CHARACTER SET charset_name] [COLLATE collation_name]</source>

== TEXT CHARACTER SET latin1 COLLATE latin1_bin==



<source lang="sql">
mysql>
mysql>
mysql> CREATE TABLE myTable
-> (
-> ID SMALLINT UNSIGNED,
-> Name VARCHAR(40),
-> Description TEXT CHARACTER SET latin1 COLLATE latin1_bin
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> desc myTable;
+-------------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------------------+------+-----+---------+-------+
| ID | smallint(5) unsigned | YES | | NULL | |
| Name | varchar(40) | YES | | NULL | |
| Description | text | YES | | NULL | |
+-------------+----------------------+------+-----+---------+-------+
3 rows in set (0.01 sec)
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql></source>

== The output from SHOW COLLATION includes all available character sets.==

It takes an optional LIKE clause that indicates which collation names to match.



<source lang="sql">
mysql>
mysql>
mysql> SHOW COLLATION LIKE "latin1%";
+-------------------+---------+----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+-------------------+---------+----+---------+----------+---------+
| latin1_german1_ci | latin1 | 5 | | Yes | 1 |
| latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 |
| latin1_danish_ci | latin1 | 15 | | Yes | 1 |
| latin1_german2_ci | latin1 | 31 | | Yes | 2 |
| latin1_bin | latin1 | 47 | | Yes | 1 |
| latin1_general_ci | latin1 | 48 | | Yes | 1 |
| latin1_general_cs | latin1 | 49 | | Yes | 1 |
| latin1_spanish_ci | latin1 | 94 | | Yes | 1 |
+-------------------+---------+----+---------+----------+---------+
8 rows in set (0.00 sec)</source>

== The SHOW CHARACTER SET command shows all available character sets.==

It takes an optional LIKE clause that indicates which character set names to match.



<source lang="sql">
mysql>
mysql>
mysql> SHOW CHARACTER SET LIKE "latin%";
+---------+-----------------------------+-------------------+--------+
| Charset | Description | Default collation | Maxlen |
+---------+-----------------------------+-------------------+--------+
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
+---------+-----------------------------+-------------------+--------+
4 rows in set (0.00 sec)
mysql>
mysql></source>

== The SHOW COLUMNS statement displays the collations of a table"s columns when invoked as SHOW FULL COLUMNS==

Columns with CHAR, VARCHAR, or TEXT data types have collations.
Numeric and other non-character types have no collation (indicated by NULL as the Collation value).



<source lang="sql">
mysql>
mysql>
mysql>
mysql>
mysql> CREATE TABLE myTable
-> (
-> c1 CHAR(10)
-> ) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> desc myTable;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| c1 | char(10) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
1 row in set (0.00 sec)
mysql>
mysql> SHOW FULL COLUMNS FROM myTable\G
*************************** 1. row ***************************
Field: c1
Type: char(10)
Collation: latin1_danish_ci
Null: YES
Key:
Default: NULL
Extra:
Privileges: select,insert,update,references
Comment:
1 row in set (0.00 sec)
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql></source>

== Using alter command to change characgter set==



<source lang="sql">
mysql> CREATE TABLE myTable
-> (
-> col1 CHAR(10)
-> ) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql>
mysql> ALTER TABLE myTable MODIFY col1 CHAR(50) CHARACTER SET greek;
Query OK, 0 rows affected (0.03 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> ALTER TABLE myTable MODIFY col1 CHAR(50) CHARACTER SET utf8;
Query OK, 0 rows affected (0.03 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql></source>

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