Additional Resources •UCA-based collations for Unicode character sets. •Binary ( xxx _bin ) collations. The following sections describe how to add user-defined collations of the first two types to existing character sets. All existing character sets already have a binary collation, so there is no need here to describe how to add one. Redefining built-in collations is not supported and may result in unexpected server behavior. Summary of the procedure for adding a new user-defined collation: The instructions here cover only user-defined collations that can be added without recompiling MySQL. To add a collation that does require recompiling (as implemented by means of functions in a C source file), use the instructions in Section 10.13, “Adding a Character Set” . However, instead of adding all the information required for a complete character set, just modify the appropriate files for an existing character set. That is, based on what is already present for the character set’s current collations, add data structures, functions, and configuration information for the new collation. If you modify an existing user-defined collation, that may affect the ordering of rows for indexes on columns that use the collation. In this case, rebuild any such indexes to avoid problems such as incorrect query results. See Section 2.11.13, “Rebuilding or Repairing Tables or Indexes” . This kind of collation is implemented using an array of 256 weights that defines a one-to-one mapping from character codes to weights.  latin1_swedish_ci  is an example. It is a case-insensitive collation, so the uppercase and lowercase versions of a character have the same weights and they compare as equal. MySQL implements several types of collations: Warning 1. Choose a collation ID. 2. Add configuration information that names the collation and describes the character-ordering rules. 3. Restart the server. 4. Verify that the server recognizes the collation. •Example showing how to add a collation for full-text searches: Section 12.10.7, “Adding a User-Defined Collation for Full-Text Indexing” •The Unicode Collation Algorithm (UCA) specification: http://www.unicode.org/reports/tr10/ •The Locale Data Markup Language (LDML) specification: http://www.unicode.org/reports/tr35/ Note Additional Resources 10.14.1 Collation Implementation Types Simple collations for 8-bit character sets 1992