>Hi everybody,
>
>I'm just wondering what would be better in your opinion:
>

>SELECT Registration.*, Schools.SchoolPhone
>		FROM dbo.Registration LEFT JOIN Schools ON Registration.School = Schools.School
>AND Schools.SiteID = @SiteID
>        WHERE RegistrationID = @RegistrationID

>
>or
>

>SELECT Registration.*, Schools.SchoolPhone
>		FROM dbo.Registration LEFT JOIN Schools ON Registration.School = Schools.School
>AND Registration.SiteID = Schools.SiteID
>        WHERE RegistrationID = @RegistrationID

>
>In other words, is it better to use parameter or field value? In the first case I would need to adjust several pages to add an extra parameter.
>
>Thanks a lot in advance.
>
>On the second thought - why do I care for one record return? LOL.

It depends what you want. When you use variable and use it in JOIN you will filter joined table for only these records that match the variable. If you use Table Field in join you will filter matching fields no matter what value they have:

Registration:
SiteId    School
-------------------------------
1         1
2         1 
3         1 
4         2
5         2

Schools:
SiteId      School 
-------------------------------
1            1
2            1

So this:

SELECT *
       FROM Registration
LEFT JOIN Schools ON Registration.School = Schools.School AND
          Registration.SiteId = Schools.SiteId

will give you this:

Schools:
SiteId      School SiteId      School 
-------------------------------------
1            1       1          1
2            1       2          1
3            1      NULL      NULL 
4            2      NULL      NULL 
5            2      NULL      NULL 

But:

DECLARE @SiteId int 
SET @SiteId = 1
SELECT *
       FROM Registration
LEFT JOIN Schools ON Registration.School = Schools.School AND
          Schools.SiteId = @SiteId

will give you this:

Schools:
SiteId      School SiteId      School 
-------------------------------------
1            1       1          1
2            1      NULL      NULL 
3            1      NULL      NULL 
4            2      NULL      NULL 
5            2      NULL      NULL