Difference between revisions of "Query Mode"

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<p>The query mode of the [[Language Bindings]] allows you to bind external variables to a query
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<p>The query mode of the [[Clients]] allows you to bind external variables to a query
and evaluate the query in an iterative manner. For this, you need to call the <code>query()</code> function
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and evaluate the query in an iterative manner. The <code>query()</code> function of the
of the <code>Session</code> instance with your defined query. This will return a query object,
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<code>Session</code> instance returns a new query instance.</p>
which comes with a forward-only iterator. Variables can be bound to the query using the
 
<code>bind()</code> function of the query object.</p>  
 
 
   
 
   
 
==Usage==  
 
==Usage==  
 
   
 
   
<p>The query execution works as follows:</p>
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The query execution works as follows:
 
   
 
   
 
# Create a new session instance with hostname, port, username and password.
 
# Create a new session instance with hostname, port, username and password.
# Call the <code>query()</code> function of the session with the query as argument to get your query object.
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# Call <code>query()</code> with your XQuery expression to get a query object.
# Optionally bind variables to the query with the <code>bind()</code> function.
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# Optionally bind variables to the query with one of the <code>bind()</code> functions.
# Initialize query output via <code>init()</code>.
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# Optionally bind a value to the context item via <code>context()</code>.
# Iterate through the query object with the <code>more()</code> and <code>next()</code> functions. If an error occurs, an exception is thrown.
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# Iterate through the query object with the <code>more()</code> and <code>next()</code> functions.
# As an alternative, call <code>execute()</code> to get the whole result at a time. This will be faster in most cases, as the socket communication will be limited to a single call.
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# As an alternative, call <code>execute()</code> to get the whole result at a time.
# Optionally, call <code>info()</code> to get information on the number of results, query time, etc.
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# <code>info()</code> gives you information on query evaluation.
# Close the query with <code>close()</code>.
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# <code>options()</code> returns the query serialization parameters.
 +
# Don't forget to close the query with <code>close()</code>.
  
==Example in [https://svn.uni-konstanz.de/dbis/basex/trunk/api/etc/php/ PHP]==
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==PHP Example==
 +
 
 +
Taken from our [https://github.com/BaseXdb/basex-api/blob/master/src/main/php/QueryBindExample.php repository]:
  
 
<pre class="brush:php">
 
<pre class="brush:php">
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  * Documentation: http://basex.org/api
 
  * Documentation: http://basex.org/api
 
  *
 
  *
  * (C) BaseX Team 2005-11, ISC License
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  * (C) BaseX Team 2005-15, BSD License
 
  */
 
  */
 
include("BaseXClient.php");
 
include("BaseXClient.php");
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     $query->bind("$name", "number");
 
     $query->bind("$name", "number");
  
     // initialize query
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     // print result
    print $query->init();
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     print $query->execute()."\n";
 
 
    // loop through all results
 
     while($query->more()) {
 
      print $query->next()."\n";
 
    }
 
  
 
     // close query instance
 
     // close query instance
     print $query->close();
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     $query->close();
  
 
   } catch (Exception $e) {
 
   } catch (Exception $e) {
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</pre>
 
</pre>
  
[[Category:Developer]]
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=Changelog=
[[Category:Server]]
+
 
[[Category:Bindings]]
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;Version 7.2
 +
 
 +
* Added: {{Code|context()}} function

Revision as of 14:53, 17 January 2016

The query mode of the Clients allows you to bind external variables to a query and evaluate the query in an iterative manner. The query() function of the Session instance returns a new query instance.

Usage

The query execution works as follows:

  1. Create a new session instance with hostname, port, username and password.
  2. Call query() with your XQuery expression to get a query object.
  3. Optionally bind variables to the query with one of the bind() functions.
  4. Optionally bind a value to the context item via context().
  5. Iterate through the query object with the more() and next() functions.
  6. As an alternative, call execute() to get the whole result at a time.
  7. info() gives you information on query evaluation.
  8. options() returns the query serialization parameters.
  9. Don't forget to close the query with close().

PHP Example

Taken from our repository:

<?php
/*
 * This example shows how queries can be executed in an iterative manner.
 * Documentation: http://basex.org/api
 *
 * (C) BaseX Team 2005-15, BSD License
 */
include("BaseXClient.php");

try {
  // create session
  $session = new Session("localhost", 1984, "admin", "admin");
  
  try {
    // create query instance
    $input = 'declare variable $name external; '.
      'for $i in 1 to 10 return element { $name } { $i }';
    $query = $session->query($input);

    // bind variable
    $query->bind("$name", "number");

    // print result
    print $query->execute()."\n";

    // close query instance
    $query->close();

  } catch (Exception $e) {
    // print exception
    print $e->getMessage();
  }

  // close session
  $session->close();

} catch (Exception $e) {
  // print exception
  print $e->getMessage();
}
?>

Changelog

Version 7.2
  • Added: context() function