sql procedure

/*Procedure*/
ALTER PROC sp_TUI
@pkg_Code VARCHAR(20),
@bid int,
@p_name VARCHAR(20)
AS
BEGIN
SET @pkg_Code=REPLACE(@pkg_Code,'null','')
SET @p_name=REPLACE(@p_name,'null','')
SELECT b_id 'Booking Reference',title 'Lead Pax Title',first_name 'Lead Pax 1st Name',last_name 'Lead Pax 2nd Name',age 'Lead Pax Age',a_code 'Agent Code',
a_name 'Agent name',branch_code 'Branch Code',region_code 'Region Code',Channel,p_Code 'Product Code',b_Type 'Booking Type',p_Type 'Product Type',
pkg_Code 'Package Code',pkg_Name 'Package Name',b_Booking_Date 'Booking Date',b_Dep_Date 'Departure Date',b_No_of_Adults 'No of Adults',
b_No_of_Childs 'No of Childs',b_No_of_Infants 'No of Infants',outbond_dep_airport 'Outbound Departure Airport',outbond_Arrival_airport 'Outbound Arrival Airport',
inbond_dep_airport 'Inbound Departure Airport',inbond_Arrival_airport 'Inbound Arrival Airport',S_Type 'Service Type',s_Code 'Service Code',s_name 'Service Name',S_Dep 'Service Departure',
S_Arr 'Service Arrival',S_Cost 'Service Cost',S_Sale_price 'Service Sale Price',S_Margin 'Service Margin',S_Margin_percent 'Service Marging %',total_booking_cost 'Total Booking Cost',
booking_margin 'Booking Margin',booking_marging_percent 'Booking margin %',p_Name 'Product name',mobile 'Opp Mobile',email 'Opp Email',
booking_confirmed,
pli_days 'Day'
FROM Booking   
JOIN Product  ON Booking.p_id_r=Product.p_id  
JOIN Opportunity ON Booking.opp_id_r=Opportunity.opp_id
JOIN Package  ON Booking.pkg_id=Package.pkg_id  
JOIN TUI_Service ON Booking.b_id=TUI_Service.b_id_r
JOIN Package_Line_Item ON TUI_Service.pkg_line_item_id_r=Package_Line_Item.pkg_line_item_id
JOIN Agent  ON Booking.a_id_r=Agent.a_id

where (pkg_Code=@pkg_Code OR ISNULL(@pkg_Code,'')='')
AND (p_Name=@p_name OR ISNULL(@p_name,'')='')
AND CASE WHEN @bid != 0
    THEN
        b_id
    ELSE
        @bid
    END
    =
    CASE WHEN @bid != 0
    THEN
        @bid
    ELSE
        @bid
    END

--GROUP BY p_Name, pkg_Name, b_id
ORDER BY p_Name, pkg_Name, b_id

END

--exec sp_TUI NULL,14,Null