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 12.6.1 Boolean Full-Text Searches
 As of Version 4.0.1, MySQL can also perform boolean full-text searches
 using the `IN BOOLEAN MODE' modifier.
      mysql> SELECT * FROM articles WHERE MATCH (title,body)
          -> AGAINST ('+MySQL -YourSQL' IN BOOLEAN MODE);
      | id | title                 | body                                |
      |  1 | MySQL Tutorial        | DBMS stands for DataBase ...        |
      |  2 | How To Use MySQL Well | After you went through a ...        |
      |  3 | Optimizing MySQL      | In this tutorial we will show ...   |
      |  4 | 1001 MySQL Tricks     | 1. Never run mysqld as root. 2. ... |
      |  6 | MySQL Security        | When configured properly, MySQL ... |
 This query retrieves all the rows that contain the word "MySQL" but
 that do _not_ contain the word "YourSQL".
 Boolean full-text searches have these characteristics:
    * They do not use the 50% threshold.
    * They do not automatically sort rows in order of decreasing
      relevance.  You can see this from the preceding query result: The
      row with the highest relevance is the one that contains "MySQL"
      twice, but it is listed last, not first.
    * They can work even without a `FULLTEXT' index, although this would
      be _slow_.
    * The minimum and maximum word length full-text parameters apply.
    * The stopword list applies.
 The boolean full-text search capability supports the following
      A leading plus sign indicates that this word _must be_ present in
      every row returned.
      A leading minus sign indicates that this word _must not be_
      present in any row returned.
 `(no operator)'
      By default (when neither `+' nor `-' is specified) the word is
      optional, but the rows that contain it will be 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 row.  The `>' operator
      increases the contribution and the `<' operator decreases it.  See
      the example below.
 `( )'
      Parentheses are used to 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 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.
      A phrase that is enclosed within double quote (`"') characters
      matches only rows that contain the phrase _literally, as it was
 The following examples demonstrate some search strings that use boolean
 full-text operators:
 `'apple banana''
      Find rows that contain at least one of the two words.
 `'+apple +juice''
      Find rows that contain both words.
 `'+apple macintosh''
      Find rows that contain the word "apple", but rank rows higher if
      they also contain "macintosh".
 `'+apple -macintosh''
      Find rows that contain the word "apple" but not "macintosh".
 `'+apple +(>turnover <strudel)''
      Find rows that contain the words "apple" and "turnover", or
      "apple" and "strudel" (in any order), but rank "apple turnover"
      higher than "apple strudel".
      Find rows that contain words such as "apple", "apples",
      "applesauce", or "applet".
 `'"some words"''
      Find rows that contain the exact phrase "some words" (for example,
      rows that contain "some words of wisdom" but not "some noise
      words").  Note that the `"' characters that surround the phrase
      are operator characters that delimit the phrase.  They are not the
      quotes that surround the search string itself.
      The full-text engine splits the phrase into words, performs a
      search in the `FULLTEXT' index for the words, and then performs a
      substring search for the phrase in the records that are found. If
      the phrase contains no words that are in the index, the result
      will be empty. For example, if all words are either stopwords or
      shorter than the minimum length of indexed words, the result will
      be empty.
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