A leading minus sign indicates that this word must not be
present in any row returned. By default (when neither plus nor minus
is specified) the word is optional, but the rows that contain it will
be rated higher.
<>
These two operators are used to change a word's contribution to
the relevance value that is assigned to a row. The < operator
decreases the contribution and the > operator increases it. See the
example below.
()
Parentheses are used to group words into subexpressions.
~
A leading tilde acts as a negation operator, causing the word's
contribution to the row relevance to be negative. It's useful for
marking noise words. A row that contains such a word will be rated
lower than others, but will not be excluded altogether, as it would
be with the - operator.
*
An asterisk is the truncation operator. Unlike the other
operators, it should be appended to the word, not prepended.
"
The phrase, that is enclosed in double quotes ", matches only
rows that contain this phrase literally, as it was typed.