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MySQL 8.4 Reference Manual  /  ...  /  Adding a UCA Collation to a Unicode Character Set

12.14.4 Adding a UCA Collation to a Unicode Character Set

This section describes how to add a UCA collation for a Unicode character set by writing the <collation> element within a <charset> character set description in the MySQL Index.xml file. The procedure described here does not require recompiling MySQL. It uses a subset of the Locale Data Markup Language (LDML) specification, which is available at With this method, you need not define the entire collation. Instead, you begin with an existing base collation and describe the new collation in terms of how it differs from the base collation. The following table lists the base collations of the Unicode character sets for which UCA collations can be defined. It is not possible to create user-defined UCA collations for utf16le; there is no utf16le_unicode_ci collation that would serve as the basis for such collations.

Table 12.4 MySQL Character Sets Available for User-Defined UCA Collations

Character Set Base Collation
utf8mb4 utf8mb4_unicode_ci
ucs2 ucs2_unicode_ci
utf16 utf16_unicode_ci
utf32 utf32_unicode_ci

The following sections show how to add a collation that is defined using LDML syntax, and provide a summary of LDML rules supported in MySQL.