Bug 161191 Null is inserted when drag columns to query text with ctrl key pressed
Description: Null is inserted when drag columns to query text with ctrl key pressed Steps to reproduce: 1. New a data source. 2. New a dataset. 3. Press and hold ctrl key, select OFFICECODE and CITY columns, drag to query text. Expected result: "CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted in query text. Actual result: "null,CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted
data/org.eclipse.birt.report.data.oda.jdbc.ui/src/org/eclipse/birt/report/data/oda/jdbc/ui/editors/SQLDataSetEditorPage.java
}
		}
		catch ( SQLException e )
		{
			e.printStackTrace( );
		}
		return allSchemas;
	}
	
	/**
	 * 
	 * @return The Type of the object selected in the type combo ( Can be one of the following )
	 *   1) TABLE
	 *   2) VIEW
	 *   3) ALL
	 */
	private String  getSelectedDbType()
	{
		
		IStructuredSelection selection = (IStructuredSelection)filterComboViewer.getSelection();
		String type = DbType.ALL_STRING;
		if(selection != null && selection.getFirstElement() != null )
		{
			DbType dbType =  (DbType)selection.getFirstElement();
			
			switch ( dbType.getType())
			{
				case DbType.TABLE_TYPE:
					type = DbType.TABLE_STRING;
					break;