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query_script_loop_while.html
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query_script_loop_while.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>query_script_loop_while: common_schema documentation</title>
<meta name="description" content="query_script_loop_while: common_schema" />
<meta name="keywords" content="query_script_loop_while: common_schema" />
<link rel="stylesheet" type="text/css" href="css/style.css" />
</head>
<body>
<div id="main">
<div id="header">
<h1>common_schema</h1> <strong>2.2</strong> documentation
<div class="subtitle">DBA's framework for MySQL</div>
</div>
<div id="contentwrapper">
<div id="content">
<h2><a href="query_script_loop_while.html">query_script_loop_while</a></h2>
<p>
QueryScript Flow Control: <strong>loop-while</strong> statement
</p>
<h3>SYNOPSIS</h3>
<p>
<blockquote><pre>loop
statement;
while (expression);
</pre></blockquote>
</p>
<h3>DESCRIPTION</h3>
<p>
<i>loop-while</i> is a flow control looping structure. It makes for a condition test based on
a given <a href="query_script_expressions.html">expression</a>.
</p>
<p>
As opposed to <a href="query_script_while.html">while</a>, <i>loop-while</i> tests the
expression <i>after</i> each statement execution. As result, the loop iterates at least once.
</p>
<p>
The <i>loop-while</i> loop terminates in the following cases:
<ul>
<li>The <i>expression</i> does not hold true</li>
<li>A <a href="query_script_break.html">break</a> statement is executed inside the loop (but not inside a nested loop)</li>
<li>A <a href="query_script_return.html">return</a> statement is executed inside the loop</li>
<li>An uncaught error is raised (at the moment all errors are by default uncaught unless handled in user code)</li>
</ul>
Of course, any error terminates the entire script execution, including any loops.
</p>
<p>
Empty statements are not allowed in QueryScript. However, empty blocks are, and the
<i>loop-while</i> clause may be followed by an empty block, or by the do-nothing <a href="query_script_pass.html">pass</a> statement.
</p>
<h3>EXAMPLES</h3>
<p>
Generate Fibonacci sequence:
<blockquote><pre>
var $n1, $n2, $n3, $seq;
set $n1 := 1, $n2 := 0, $n3 := NULL;
set $seq := '';
loop
{
set $n3 := $n1 + $n2;
set $n1 := $n2;
set $n2 := $n3;
set $seq := CONCAT($seq, $n3, ', ');
}
while ($n3 < 100);
SELECT $seq AS fibonacci_numbers;
+---------------------------------------------+
| fibonacci_numbers |
+---------------------------------------------+
| 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, |
+---------------------------------------------+
</pre></blockquote>
</p>
<h3>SEE ALSO</h3>
<a href="query_script_if_else.html">if-else</a>,
<a href="query_script_while.html">while</a>,
<a href="query_script_foreach.html">foreach</a>,
<a href="query_script_expressions.html">expressions</a>,
<a href="query_script_break.html">break</a>
<h3>AUTHOR</h3>
Shlomi Noach
<br/>
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Search online documentation
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onsubmit="document.forms['search_form']['q'].value = 'site:http://common-schema.googlecode.com/svn/trunk/common_schema/doc/html/ '+document.forms['search_form']['search_term'].value;">
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<div id="menu">
<ul>
<li><a title="Introduction" href="introduction.html">Introduction</a></li>
<li><a title="Documentation" href="documentation.html">Documentation</a></li>
<li><a title="Download" href="download.html">Download</a></li>
<li><a title="Install" href="install.html">Install</a></li>
<li><a title="Risks" href="risks.html">Risks</a></li>
</ul>
<h3>QUERY SCRIPT</h3>
<ul>
<li><a title="QueryScript" href="query_script.html">QueryScript</a></li>
<li><a title="Execution" href="query_script_execution.html">Execution</a></li>
<li><a title="Flow control" href="query_script_flow_control.html">Flow control</a></li>
<li><a title="Statements" href="query_script_statements.html">Statements</a></li>
<li><a title="Expressions" href="query_script_expressions.html">Expressions</a></li>
<li><a title="Variables" href="query_script_variables.html">Variables</a></li>
</ul>
<h3>DEBUG</h3>
<ul>
<li><a title="rdebug" href="rdebug.html">rdebug</a></li>
<li><a title="rdebug API" href="rdebug_api.html">rdebug API</a></li>
<li><a title="rdebug workflow" href="rdebug_workflow.html">Workflow</a></li>
</ul>
<h3>ROUTINES</h3>
<ul>
<li><a title="Execution & flow control" href="execution_routines.html">Execution & flow control</a></li>
<li><a title="General" href="general_routines.html">General</a></li>
<li><a title="Process" href="process_routines.html">Process</a></li>
<li><a title="Query analysis" href="query_analysis_routines.html">Query analysis</a></li>
<li><a title="Schema analysis" href="schema_analysis_routines.html">Schema analysis</a></li>
<li><a title="Security" href="security_routines.html">Security</a></li>
<li><a title="Text" href="text_routines.html">Text</a></li>
<li><a title="Time & date" href="temporal_routines.html">Time & date</a></li>
<li><a title="Charting" href="charting_routines.html">Charting</a></li>
</ul>
<h3>VIEWS</h3>
<ul>
<li><a title="Schema analysis" href="schema_analysis_views.html">Schema analysis</a></li>
<li><a title="Data dimension" href="data_dimension_views.html">Data dimension</a></li>
<li><a title="Process" href="process_views.html">Process</a></li>
<li><a title="Security" href="security_views.html">Security</a></li>
<li><a title="Monitoring" href="monitoring_views.html">Monitoring</a></li>
<li><a title="InnoDB Plugin" href="innodb_plugin_views.html">InnoDB Plugin</a></li>
<li><a title="Percona server" href="percona_server_views.html">Percona Server</a></li>
<li><a title="TokuDB" href="tokudb_views.html">TokuDB</a></li>
</ul>
<h3>DATA</h3>
<ul>
<li><a title="tables" href="tables.html">Tables</a></li>
<li><a title="variables" href="variables.html">Variables</a></li>
</ul>
<h3>META</h3>
<ul>
<li><a title="Help" href="help.html">help</a></li>
<li><a title="Metadata" href="metadata.html">metadata</a></li>
<li><a title="status" href="status.html">status</a></li>
</ul>
</div>
</div>
<div class="clear"> </div>
<div id="footnote" align="center">
<a href="">common_schema</a> documentation
</div>
</div>
</div>
</body>
</html>