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Comment:Add a description of the "^" syntax to fts5.in.
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User & Date: dan 2017-11-25 14:02:15
Context
2017-11-25
15:22
Update the fts5 documentation to make it clear that the xDestroy function is not invoked if either xCreateFunction or xCreateTokenizer fails. check-in: 820de7c995 user: dan tags: trunk
14:02
Add a description of the "^" syntax to fts5.in. check-in: 58bbcf8b2f user: dan tags: trunk
2017-11-13
23:06
Continuing work on the walformat.html document. check-in: 74c71c744b user: drh tags: trunk
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The following block contains a summary of the FTS query syntax in BNF form.
A detailed explanation follows.

<codeblock>
&lt;phrase&gt;    := string &#91;*]
&lt;phrase&gt;    := &lt;phrase&gt; + &lt;phrase&gt;
&lt;neargroup&gt; := NEAR ( &lt;phrase&gt; &lt;phrase&gt; ... &#91;, N] )
&lt;query&gt;     := &#91; &#91;-] &lt;colspec&gt; :] &lt;phrase&gt;
&lt;query&gt;     := &#91; &#91;-] &lt;colspec&gt; :] &lt;neargroup&gt;
&lt;query&gt;     := &#91; &#91;-] &lt;colspec&gt; :] ( &lt;query&gt; )
&lt;query&gt;     := &lt;query&gt; AND &lt;query&gt;
&lt;query&gt;     := &lt;query&gt; OR &lt;query&gt;
&lt;query&gt;     := &lt;query&gt; NOT &lt;query&gt;
&lt;colspec&gt;   := colname
&lt;colspec&gt;   := { colname1 colname2 ... }
................................................................................
</codeblock>

<p>The final query in the block above may not work as expected. Because the
"*" character is inside the double-quotes, it will be passed to the tokenizer,
which will likely discard it (or perhaps, depending on the specific tokenizer
in use, include it as part of the final token) instead of recognizing it as
a special FTS character.



















<h2 tags="FTS5 NEAR queries">FTS5 NEAR Queries</h2>

<p>Two or more phrases may be grouped into a <b>NEAR group</b>. A NEAR group
is specified by the token "NEAR" (case sensitive) followed by an open
parenthesis character, followed by two or more whitespace separated phrases, optionally followed by a comma and the numeric parameter <i>N</i>, followed by
a close parenthesis. For example:







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The following block contains a summary of the FTS query syntax in BNF form.
A detailed explanation follows.

<codeblock>
&lt;phrase&gt;    := string &#91;*]
&lt;phrase&gt;    := &lt;phrase&gt; + &lt;phrase&gt;
&lt;neargroup&gt; := NEAR ( &lt;phrase&gt; &lt;phrase&gt; ... &#91;, N] )
&lt;query&gt;     := &#91; &#91;-] &lt;colspec&gt; :] &#91;&#94;] &lt;phrase&gt;
&lt;query&gt;     := &#91; &#91;-] &lt;colspec&gt; :] &lt;neargroup&gt;
&lt;query&gt;     := &#91; &#91;-] &lt;colspec&gt; :] ( &lt;query&gt; )
&lt;query&gt;     := &lt;query&gt; AND &lt;query&gt;
&lt;query&gt;     := &lt;query&gt; OR &lt;query&gt;
&lt;query&gt;     := &lt;query&gt; NOT &lt;query&gt;
&lt;colspec&gt;   := colname
&lt;colspec&gt;   := { colname1 colname2 ... }
................................................................................
</codeblock>

<p>The final query in the block above may not work as expected. Because the
"*" character is inside the double-quotes, it will be passed to the tokenizer,
which will likely discard it (or perhaps, depending on the specific tokenizer
in use, include it as part of the final token) instead of recognizing it as
a special FTS character.

<h2 tags="FTS5 initial token queries">FTS5 Initial Token Queries</h2>
<p>
If a "&#94;" character appears immediately before a phrase that is not part of a
NEAR query, then that phrase only matches a document only if it starts at the
first token in a column. The "&#94;" syntax may be combined with a 
[FTS5 column filters|column filter], but may not be inserted into the middle of
a phrase.

<codeblock>
  ... MATCH '&#94;one'              <i>-- first token in any column must be "one"</i>
  ... MATCH '&#94; one + two'       <i>-- phrase "one two" must appear at start of a column</i>
  ... MATCH '&#94; "one two"'       <i>-- same as previous </i>
  ... MATCH 'a : &#94;two'          <i>-- first token of column "a" must be "two"</i>
  ... MATCH 'NEAR(&#94;one, two)'   <b>-- syntax error! </b>
  ... MATCH 'one + &#94;two'        <b>-- syntax error! </b>
  ... MATCH '"&#94;one two"'        <b>-- May not work as expected!</b>
</codeblock>

<h2 tags="FTS5 NEAR queries">FTS5 NEAR Queries</h2>

<p>Two or more phrases may be grouped into a <b>NEAR group</b>. A NEAR group
is specified by the token "NEAR" (case sensitive) followed by an open
parenthesis character, followed by two or more whitespace separated phrases, optionally followed by a comma and the numeric parameter <i>N</i>, followed by
a close parenthesis. For example: