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<h1 class="topictitle1">Supplying a parameter only once</h1>



<div><p>If you want to supply a parameter value once and use it multiple
times within a query, put it in the FROM clause with an appropriate CAST.</p>

<pre>SELECT  phonebook.* 
	FROM phonebook, (VALUES (CAST(? AS INT), CAST(? AS VARCHAR(255))))  
						AS Choice(choice, search_string)
	WHERE search_string = (case when choice = 1 then firstnme 
                 when choice=2 then lastname 
						when choice=3 then phonenumber end);</pre>

<p>This query selects what the second parameter will be compared to based
on the value in the first parameter. Putting the parameters in the FROM clause
means that they need to be applied only once to the query, and you can give
them names so that you can refer to them elsewhere in the query. In the example
above, the first parameter is given the name <em>choice</em>, and the second
parameter is given the name <em>search_string</em>.</p>

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<div class="parentlink"><strong>Parent topic:</strong> <a href="cdevtricks32436.html" title="This section provides some examples of interesting SQL features. It also includes a few non-SQL tips.">SQL tips</a></div>
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