Open PDF in a new tab in browser

Your tags indicate asp.net-mvc.

Create a controller to handle requests for the PDF file

Pseudo:

[RoutePrefix("Pdf")]
public class PdfController : Controller {
    [Route("{id}"]
    public ActionResult GetPDF(int id) {    
        //...Code to extract pdf from SQLServer and store in stream
        Stream stream = GetDataFromSQLServerById(id);
        return File(stream,"filename.pdf");
    }
}

On client

<a href="/Pdf/123456" target="_blank">
    <img src="images/pdficon.jpg">
</a>

Update:

Referencing @ChrisPratt's comment; (which I forgot to include in my answer)

The target attribute on the anchor tag is what will tell the browser to open the link in a new tab.