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MySQL 5.5 Reference Manual :: D Restrictions and Limits :: D.7 Restrictions on Character Sets
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D.7. Restrictions on Character Sets

  • Identifiers are stored in mysql database tables (user, db, and so forth) using utf8, but identifiers can contain only characters in the Basic Multilingual Plane (BMP). Supplementary characters are not allowed in identifiers.

  • The ucs2, utf16, and utf32 character sets have the following restrictions:

    • They cannot be used as a client character set, which means that they do not work for SET NAMES or SET CHARACTER SET. (See Section 9.1.4, “Connection Character Sets and Collations”.)

    • It is currently not possible to use LOAD DATA INFILE to load data files that use these character sets.

    • FULLTEXT indexes cannot be created on a column that uses any of these character sets. However, you can perform IN BOOLEAN MODE searches on the column without an index.

  • The REGEXP and RLIKE operators work in byte-wise fashion, so they are not multi-byte safe and may produce unexpected results with multi-byte character sets. In addition, these operators compare characters by their byte values and accented characters may not compare as equal even if a given collation treats them as equal.