sql server - Order Of Execution of the SQL query

Question

I am confused with the order of execution of this query, please explain me this. I am confused with when the join is applied, function is called, a new column is added with the Case and when the serial number is added. Please explain the order of execution of all this.

select Row_number() OVER(ORDER BY (SELECT 1))  AS 'Serial Number', 
    EP.FirstName,Ep.LastName,[dbo].[GetBookingRoleName](ES.UserId,EP.BookingRole) as RoleName,  
    (select top 1 convert(varchar(10),eventDate,103)from [3rdi_EventDates] where EventId=13) as EventDate,
    (CASE [dbo].[GetBookingRoleName](ES.UserId,EP.BookingRole)  
            WHEN    '90 Day Client' THEN 'DC'
            WHEN    'Association Client'  THEN  'DC'
            WHEN    'Autism Whisperer'    THEN  'DC'
            WHEN    'CampII'             THEN   'AD' 
            WHEN    'Captain'              THEN 'AD' 
            WHEN    'Chiropractic Assistant' THEN 'AD'
            WHEN    'Coaches'               THEN 'AD'
            END) as Category from [3rdi_EventParticipants] as EP  
    inner join [3rdi_EventSignup] as ES on EP.SignUpId = ES.SignUpId  
    where EP.EventId = 13
    and userid in (  
    select distinct userid from userroles  
    --where roleid not in(6,7,61,64) and roleid not in(1,2))  
    where roleid not in(19, 20, 21, 22) and roleid not in(1,2))

This is the function which is called from the above query.

CREATE function [dbo].[GetBookingRoleName]  
(  
 @UserId as integer,
 @BookingId as integer
)  
RETURNS varchar(20)  
as  
begin  
declare @RoleName varchar(20)  

if @BookingId = -1
Select Top 1 @RoleName=R.RoleName From UserRoles UR inner join Roles R on UR.RoleId=R.RoleId Where UR.UserId=@UserId and R.RoleId not in(1,2)  
else
Select @RoleName= RoleName From Roles where RoleId = @BookingId

return @RoleName  
end

Answer 1

Queries are generally processed in the follow order (SQL Server). I have no idea if other RDBMS's do it this way.

FROM [MyTable]
    ON [MyCondition]
  JOIN [MyJoinedTable]
 WHERE [...]
 GROUP BY [...]
HAVING [...]
SELECT [...]
 ORDER BY [...]