MySQL 8.4 Release Notes
标识符存储在
mysql表中（user、db等）使用utf8mb3，但标识符只能包含基础多语言平面（BMP）中的字符。标识符中不允许使用补充字符。Identifiers are stored inmysqldatabase tables (user,db, and so forth) usingutf8mb3, but identifiers can contain only characters in the Basic Multilingual Plane (BMP). Supplementary characters are not permitted in identifiers.ucs2、utf16、utf16le和utf32字符集有以下限制：Theucs2,utf16,utf16le, andutf32character sets have the following restrictions:它们都不能用作客户端字符集。请参见 不允许的客户端字符集。None of them can be used as the client character set. See Impermissible Client Character Sets.
目前无法使用
LOAD DATA来加载使用这些字符集的数据文件。It is currently not possible to useLOAD DATAto load data files that use these character sets.FULLTEXT索引不能在使用任何这些字符集的列上创建。然而，你可以在没有索引的情况下对该列执行IN BOOLEAN MODE搜索。FULLTEXTindexes cannot be created on a column that uses any of these character sets. However, you can performIN BOOLEAN MODEsearches on the column without an index.
REGEXP和RLIKE操作符以字节方式工作，因此它们不支持多字节，并且在使用多字节字符集时可能产生意外结果。此外，这些操作符按字节值比较字符，即使某个排序规则将带重音的字符视为相等，它们也可能不会被视为相等。TheREGEXPandRLIKEoperators 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.