Stored procedure - sql hjælp søges

if @Template <>''
if @Template = ''
Jeg kommer ikke ind i den del. Nogle der kan hjælpe?
Felten indeholder null, tom eller tekst.

CREATE PROCEDURE ReadTemplateInvoice
@Invoice_Number char(10)
AS
    declare @Template char(250)
    SELECT @Template = TemplateName
    FROM Invoice
    where Invoice_Number = @Invoice_Number

if @Template <>''
begin
SELECT TemplateName
FROM Invoice
where Invoice_Number = @Invoice_Number
end

if @Template = ''
begin
    SELECT    TOP 1 TemplateDefault.TemplateName
FROM        TemplateDefault INNER JOIN
                      INVOICE_LINE ON TemplateDefault.TemplateType = INVOICE_LINE.LINE_TYPE
WHERE    INVOICE_LINE.INVOICE_NUMBER = @Invoice_Number
end
GO