12.14.4 Adding a UCA Collation to a Unicode Character Set

12.14.4.1 Defining a UCA Collation Using LDML Syntax

12.14.4.2 LDML Syntax Supported in MySQL

12.14.4.3 Diagnostics During Index.xml Parsing

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 http://www.unicode.org/reports/tr35/. 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.