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		<h1 class="dtH1">Creating Dynamic Queries</h1>
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	<p>Often developers need to query database information based on input 
	received from the user interface. Depending on your application's 
	architecture, this can become somewhat of a maintenance burden. For example, 
	if your application uses stored procedures to retrieve product information, 
	you may end up writing procedures to query the Products table by CategoryID, 
	by OrderID, by SupplierID, and on and on. Later on in the application's 
	lifespan, a schema change to the Products table now requires support staff 
	to change all of the custom stored procedures. Developers are also 
	constrained by the number of columns returned by the stored procedure. What 
	if the procedure returns every column in the table, but the developer needs 
	only 1 or 2?</p>
	<p>In a multi-database scenario, developers are forced to learn the query 
	syntax of each database (SQL Server, Oracle, Access, MySQL, Firebird, etc.). 
	EasyObjects.NET provides developers an easy, database-independent query 
	syntax that works with all supported databases. A fundamental understanding 
	of database queries is still required, but not database-specific query 
	syntax.</p>
	<h2>Typical Goals</h2>
	<p>In this scenario, you want to query a database table or view load the EasyObject business object with the results, 
	without having to write custom stored procedures or database-specific inline 
	SQL.</p>
	<p>These goals can be summarized as follows: </p>
	<ul>
		<li>You want to retrieve data from a database table or view.   
		</li>
		<li>You want to specify one or more columns as part of the results in 
		order to minimize network traffic.   
		</li>
		<li>You want to specify parameters for the SQL WHERE clause in order to 
		bring back a subset of the data. 
		</li>
		<li>You want to specify columns for the SQL ORDER BY clause in order to 
		bring back the results with a custom sort order.</li>
		<li>You want the same techniques and syntax to work regardless of which 
		database platform you are using.</li>
	</ul>
	<h2>Solution</h2>
	<p>Use the <b>Query</b> object provided by the <b>DynamicQuery</b> class. 
	See the sample code below for examples.</p>
	<h2>Using Query</h2>
	<p>The following code shows how to use the <b>Query</b> object.</p>
	<p>[C#]</p>
<!-- code formatted by http://manoli.net/csharpformat/ -->
<pre class="csharpcode">
Employees emp = new Employees();

// Limit the columns returned by the SELECT query
emp.Query.AddResultColumn(EmployeesSchema.LastName);
emp.Query.AddResultColumn(EmployeesSchema.FirstName);
emp.Query.AddResultColumn(EmployeesSchema.City);
emp.Query.AddResultColumn(EmployeesSchema.Region);

// Add an ORDER BY clause
emp.Query.AddOrderBy(EmployeesSchema.LastName);

// Add a WHERE clause
emp.Where.Region.Value = &quot;WA&quot;;

emp.Query.Load();

// Bind the EasyObject's DefaultView to the DataGrid for display
this.resultsDataGrid.SetDataBinding(emp.DefaultView, null);

</pre>
	<p>[VB]</p>
<!-- code formatted by http://manoli.net/csharpformat/ -->
<pre class="csharpcode">
Dim emp As Employees = New Employees

' Limit the columns returned by the SELECT query
emp.Query.AddResultColumn(EmployeesSchema.LastName)
emp.Query.AddResultColumn(EmployeesSchema.FirstName)
emp.Query.AddResultColumn(EmployeesSchema.City)
emp.Query.AddResultColumn(EmployeesSchema.Region)

' Add an ORDER BY clause
emp.Query.AddOrderBy(EmployeesSchema.LastName)

' Add a WHERE clause
emp.Where.Region.Value = &quot;WA&quot;

emp.Query.Load()

' Bind the EasyObject's DefaultView to the DataGrid for display
Me.resultsDataGrid.SetDataBinding(emp.DefaultView, Nothing)
</pre>
	<h2>Usage Notes</h2>
	<p>Calling <b>Query.Load</b> without specifying any result columns or <b>
	Where</b> parameters is equivalent to calling <b>LoadAll</b>.</p>
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	<h4 class="dtH4">See also</h4>
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	<a href="developapps-scenarios.htm">
	Key Scenarios</a>
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