Character Set & Collate?
MySQL Character set support that enables you store data using of character set
Perform comparisons according to variety of collation
Usage
- Use at server, database, table, and column level
- used for the MyISAM, MEMORY, NDBCLUSTER, InnoDB storage engine
Issue with Character Set
- Its not only affect data storage, but also communication b/w client programs and mysql server
- If you want your client program communicated with server using different char set than default then you should need to specify
- For e.g if you need to use UTF-8, issue below statement after connecting to server
SET NAMES 'utf8'
About Character Set and collation
Character set is set of symbols and encodings, Collation is set of rules for comparing character in character set
To under stand take alpahbet A, B, a, b
- Assign each letter a number A = 0, B = 1, a = 2, b = 3
- 0 is encoding of A, combination of all four letters and their encoding is character set
- Suppose if you want compare two values A, B. Take their encoding A=0, B=1 so tell A is less than B, what we done here just apply collation to our character set
Collation is set of rule (one rule in this case) “comapre the encodings” (binary collation), like that many more complex collation defined.
In real life we know character set have many characters, with different regions…
Defualt MySQL do following things
- Store strings using variety of character sets
- Compare strings using variety of collations
- Enable specfication fo collation and character at any level
So we need to understand
- the different set of character set and collations
- how to changes the defaults
- how they affect the behaviour of String operation and functions
How Character set and Collaction in mysql
MySQL support multiple character sets.
To check available character set, use the INFORMATION_SCHEMA CHARACTER_SETS table or use SHOW CHARACTER SET statement
A given charcter set have atleast on Collation or it have several.
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 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| utf16 | UTF-16 Unicode | utf16_general_ci | 4 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| utf32 | UTF-32 Unicode | utf32_general_ci | 4 |
| 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 |
+----------+-----------------------------+---------------------+--------+
39 rows in set (0.00 sec)
To list the display collation for a character set use SHOW COLLATION, below one display Collation for UTF8 character set., Alwause one collation should be default for character set
mysql> SHOW COLLATION WHERE Charset = 'utf8';
+--------------------------+---------+-----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+--------------------------+---------+-----+---------+----------+---------+
| utf8_general_ci | utf8 | 33 | Yes | Yes | 1 |
| utf8_bin | utf8 | 83 | | Yes | 1 |
| utf8_unicode_ci | utf8 | 192 | | Yes | 8 |
| utf8_icelandic_ci | utf8 | 193 | | Yes | 8 |
| utf8_latvian_ci | utf8 | 194 | | Yes | 8 |
| utf8_romanian_ci | utf8 | 195 | | Yes | 8 |
| utf8_slovenian_ci | utf8 | 196 | | Yes | 8 |
| utf8_polish_ci | utf8 | 197 | | Yes | 8 |
| utf8_estonian_ci | utf8 | 198 | | Yes | 8 |
| utf8_spanish_ci | utf8 | 199 | | Yes | 8 |
| utf8_swedish_ci | utf8 | 200 | | Yes | 8 |
| utf8_turkish_ci | utf8 | 201 | | Yes | 8 |
| utf8_czech_ci | utf8 | 202 | | Yes | 8 |
| utf8_danish_ci | utf8 | 203 | | Yes | 8 |
| utf8_lithuanian_ci | utf8 | 204 | | Yes | 8 |
| utf8_slovak_ci | utf8 | 205 | | Yes | 8 |
| utf8_spanish2_ci | utf8 | 206 | | Yes | 8 |
| utf8_roman_ci | utf8 | 207 | | Yes | 8 |
| utf8_persian_ci | utf8 | 208 | | Yes | 8 |
| utf8_esperanto_ci | utf8 | 209 | | Yes | 8 |
| utf8_hungarian_ci | utf8 | 210 | | Yes | 8 |
| utf8_sinhala_ci | utf8 | 211 | | Yes | 8 |
| utf8_general_mysql500_ci | utf8 | 223 | | Yes | 1 |
+--------------------------+---------+-----+---------+----------+---------+
23 rows in set (0.00 sec)
Two different character can’t have same Collation
Each character set have default Collation
Collation name starts with name of the character set they associated
When a character set has multiple collations, it might not be clear which collation is most suitable for a given application. To avoid choosing an inappropriate collation, perform some comparisons with representative data values to make sure that a given collation sorts values the way you expect.