10.1.3.1 Collation Naming Conventions

MySQL collation names follow these conventions:

• A collation name starts with the name of the character set with which it is associated, generally followed by one or more suffixes indicating other collation characteristics. For example, utf8_general_ci and latin1_swedish_ci are collations for the utf8 and latin1 character sets, respectively. The binary character set has a single collation, also named binary, with no suffixes.

• A language-specific collation includes a language name. For example, utf8_turkish_ci and utf8_hungarian_ci sort characters for the utf8 character set using the rules of Turkish and Hungarian, respectively.

• Collation suffixes indicate whether a collation is case and accent sensitive, or binary. The following table shows the suffixes used to indicate these characteristics.

  Table 10.1 Collation Case Sensitivity Suffixes

  Suffix	Meaning
  _ai	Accent insensitive
  _as	Accent sensitive
  _ci	Case insensitive
  _cs	Case sensitive
  _bin	Binary

  
  

  For nonbinary collation names that do not specify accent sensitivity, it is determined by case sensitivity. If a collation name does not contain _ai or _as, _ci in the name implies _ai and _cs in the name implies _as. For example, latin1_general_ci is explicitly case insensitive and implicitly accent insensitive, and latin1_general_cs is explicitly case sensitive and implicitly accent sensitive.

  For the binary collation of the binary character set, comparisons are based on numeric byte values. For the _bin collation of a nonbinary character set, comparisons are based on numeric character code values, which differ from byte values for multibyte characters. For more information, see Section 10.1.8.5, “The binary Collation Compared to _bin Collations”.

• For Unicode character sets, collation names may include a version number to indicate the version of the Unicode Collation Algorithm (UCA) on which the collation is based. UCA-based collations without a version number in the name use the version-4.0.0 UCA weight keys. For example:

  • utf8_unicode_520_ci is based on UCA 5.2.0 weight keys (http://www.unicode.org/Public/UCA/5.2.0/allkeys.txt).

  • utf8_unicode_ci (with no version named) is based on UCA 4.0.0 weight keys (http://www.unicode.org/Public/UCA/4.0.0/allkeys-4.0.0.txt).

• For Unicode character sets, the xxx_general_mysql500_ci collations preserve the pre-5.1.24 ordering of the original xxx_general_ci collations and permit upgrades for tables created before MySQL 5.1.24 (Bug #27877).