Oracle 5.0 Reference Manual page 959

•
+
A leading plus sign indicates that this word must be present in each row that is returned.
•
-
A leading minus sign indicates that this word must not be present in any of the rows that are
returned.
Note: The operator acts only to exclude rows that are otherwise matched by other search terms.
-
Thus, a boolean-mode search that contains only terms preceded by
does not return "all rows except those containing any of the excluded terms."
• (no operator)
By default (when neither
are rated higher. This mimics the behavior of
modifier.
BOOLEAN MODE
•
> <
These two operators are used to change a word's contribution to the relevance value that is assigned
to a row. The operator increases the contribution and the
>
following this list.
•
( )
Parentheses group words into subexpressions. Parenthesized groups can be nested.
•
~
A leading tilde acts as a negation operator, causing the word's contribution to the row's relevance to
be negative. This is useful for marking "noise" words. A row containing such a word is rated lower
than others, but is not excluded altogether, as it would be with the
•
*
The asterisk serves as the truncation (or wildcard) operator. Unlike the other operators, it should
be appended to the word to be affected. Words match if they begin with the word preceding the
operator.
If a word is specified with the truncation operator, it is not stripped from a boolean query, even
if it is too short (as determined from the
occurs because the word is not seen as too short or a stopword, but as a prefix that must
be present in the document in the form of a word that begins with the prefix. Suppose that
ft_min_word_len=4
return fewer rows than a search for
• The former query remains as is and requires both
present in the document.
• The latter query is transformed to
and a stopword, and either condition is enough to cause it to be ignored.
•
"
A phrase that is enclosed within double quote (""") characters matches only rows that contain the
phrase literally, as it was typed. The full-text engine splits the phrase into words and performs a
search in the
FULLTEXT
substring search for the phrase in the records that were found, so the match must include nonword
characters in the phrase. As of MySQL 5.0.3, nonword characters need not be matched exactly:
Phrase searching requires only that matches contain exactly the same words as the phrase and in
Boolean Full-Text Searches
nor is specified) the word is optional, but the rows that contain it
+ -
MATCH() ... AGAINST()
ft_min_word_len
[452]. ft_min_word_len=4. Then a search for
'+word +the':
(requiring only
+word
index for the words. Prior to MySQL 5.0.3, the engine then performed a
939
returns an empty result. It
-
[934]
operator decreases it. See the example
<
operator.
-
[452] setting) or a stopword. This
'+word +the*'
and (a word starting with the) to be
word the*
to be present).
word
without the
IN
*
will likely
is both too short
the