+
A leading plus sign indicates that this word must be present in each result that is returned.

-
A leading minus sign indicates that this word must not be present in any of the results that are returned.

Note: The - operator acts only to exclude results that are otherwise matched by other search terms. Thus, a boolean-mode search that contains only terms preceded by - returns an empty result. It does not return “all results except those containing any of the excluded terms.”

(no operator)
By default (when neither + nor - is specified) the word is optional, but the results that contain it are rated higher. This mimics the behavior of MATCH() ... AGAINST() without the IN BOOLEAN MODE modifier.

> <
These two operators are used to change a word's contribution to the relevance value that is assigned to a result. The > operator increases the contribution and the < operator decreases it. See the example 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 result's relevance to be negative. This is useful for marking “noise” words. A result containing such a word is rated lower than others, but is not excluded altogether, as it would be with the - operator.

*
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.

"
A phrase that is enclosed within double quote (‘"’) characters matches only results that contain the phrase literally, as it was typed. The full-text engine splits the phrase into words, performs a search in the FULLTEXT index for the words. The engine then performs a substring search for the phrase in the records that are found, so the match must include non-word characters in the phrase. For example, "test phrase" does not match "test, phrase".

If the phrase contains no words that are in the index, the result is empty. For example, if all words are either stopwords or shorter than the minimum length of indexed words, the result is empty.

The following examples demonstrate some search strings that use boolean full-text operators:

apple banana

Find results that contain at least one of the two words.

+apple +juice

Find results that contain both words.

+apple macintosh

Find results that contain the word “apple”, but rank results higher if they also contain “macintosh”.

+apple -macintosh

Find results that contain the word “apple” but not “macintosh”.

+apple ~macintosh

Find results that contain the word “apple”, but if the result also contains the word “macintosh”, rate it lower than if result does not. This is “softer” than a search for +apple -macintosh, for which the presence of “macintosh” causes the result not to be returned at all.

+apple +(>turnover <strudel)

Find results that contain the words “apple” and “turnover”, or “apple” and “strudel” (in any order), but rank “apple turnover” higher than “apple strudel”.

apple*

Find results that contain words such as “apple”, “apples”, “applesauce”, or “applet”.

"some words"

Find results that contain the exact phrase “some words” (for example, results that contain “some words of wisdom” but not “some noise words”). Note that the ‘"’ characters that enclose the phrase are operator characters that delimit the phrase. They are not the quotes that enclose the search string itself.

Acknowledgements:

This document was taken from www.mysql.com
(http://dev.mysql.com/doc/refman/4.1/en/fulltext-boolean.html)