+  A leading plus sign indicates that this word must be present in every row returned. +apple +juice ...both words
 -  A leading minus sign indicates that this word must not be present in any row returned. +apple -macintosh ... word 'apple' but not 'macintosh'.
 < >  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. +apple +(< turnover > strudel) ... ``apple'' and ``turnover'', or ``apple'' and ``strudel'' (in any order), but rank ``apple pie'' higher than ``apple strudel''.
 ( )  Parentheses are used to group words into subexpressions. +apple (turnover strudel)
 ~  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. +apple ~macintosh ... word 'apple' and rows with 'macintosh' come lowest.
 *  An asterisk is a wildcard. Unlike the other operators, it should be appended to the word, not prepended. apple* ... ``apple'', ``apples'', ``applesauce'', and ``applet''.
 "  The phrase, that is enclosed in double quotes ", matches only rows that contain this phrase literally, as it was typed. "some words" ... ``some words of wisdom'', but not ``some noise words''.