MySQL 5.0 Reference Manual  /  Restrictions and Limits  /  Restrictions on Character Sets

C.6 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 permitted in identifiers.

  • The ucs2 character sets has the following restrictions:

    • It cannot be used as a client character set, which means that it does not work for SET NAMES or SET CHARACTER SET. (See Section 10.1.4, “Connection Character Sets and Collations”.)

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

    • FULLTEXT indexes cannot be created on a column that this character set. 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 multibyte safe and may produce unexpected results with multibyte 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.

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