12.9.5 Full-Text Restrictions

Full-text searches can be used with most multibyte character
sets. The exception is that for Unicode, the
utf8 character set can be used, but not
the ucs2 character set. Although
FULLTEXT indexes on
ucs2 columns cannot be used, you can
perform IN BOOLEAN MODE searches on a
ucs2 column that has no such index.

The remarks for utf8 also apply to
utf8mb4, and the remarks for
ucs2 also apply to
utf16, utf16le, and
utf32.

Ideographic languages such as Chinese and Japanese do not
have word delimiters. Therefore, the built-in full-text
parser cannot determine where words begin and end
in these and other such languages.

A character-based ngram full-text parser that supports
Chinese, Japanese, and Korean (CJK), and a word-based MeCab
parser plugin that supports Japanese are provided for use
with InnoDB and MyISAM
tables.

Although the use of multiple character sets within a single
table is supported, all columns in a
FULLTEXT index must use the same
character set and collation.

The MATCH() column list must
match exactly the column list in some
FULLTEXT index definition for the table,
unless this MATCH() is
IN BOOLEAN MODE on a
MyISAM table. For
MyISAM tables, boolean-mode searches can
be done on nonindexed columns, although they are likely to
be slow.

The argument to AGAINST() must be a
string value that is constant during query evaluation. This
rules out, for example, a table column because that can
differ for each row.

For InnoDB, all DML operations
(INSERT,
UPDATE,
DELETE) involving columns
with full-text indexes are processed at transaction commit
time. For example, for an INSERT
operation, an inserted string is tokenized and decomposed
into individual words. The individual words are then added
to full-text index tables when the transaction is committed.
As a result, full-text searches only return committed data.

The '%' character is not a supported wildcard character for
full-text searches.