Finally i managed to achieve it in the XSLTSearch file itselt.

What I did is :

Added C# code to get the data from the database. Registered that into the XSLT. Append that data with XSLT Search match nodes.

Below is the code for that :

Get the data from database using below code :

    <msxsl:script language="C#" implements-prefix="ps">
     public System.Xml.XmlDocument GetList(string str, string delimiter,string searchText)
    {
        string[] items = str.Split(delimiter.ToCharArray(), StringSplitOptions.None);
        System.Xml.XmlDocument doc = new System.Xml.XmlDocument();
        doc.AppendChild(doc.CreateElement("root"));
        using (System.Xml.XmlWriter writer = doc.DocumentElement.CreateNavigator().AppendChild())
        {
// Put code here to add database data

            foreach (string item in items)
            {
                writer.WriteElementString("item", item);
            }
            writer.WriteElementString("item", searchText);
        }
        return doc;
    }
    </msxsl:script>

Get the list in the XSLT :

<!--Get the search data from the Database-->
  <xsl:variable name="xmlData" select="msxml:node-set(ps:GetList('one,two,three,four,five,six', ',',$search)/*)"></xsl:variable>

Hope this will work if anyone needs to add this king of functionality.

Regards,

Urvish Mandaliya