SQL Server Query optimisation question

I have the following queries, and I would love to find a better way to do this as it doesn't seem right the way I am doing it...

EDIT

Sorry I did not specify that I only want to return adverts that actually match all amenities!

SELECT TOP 50 Advert.Id
FROM Advert 
WHERE Id in(SELECT Advert_id FROM AdvertsToAmenities WHERE Amenity_id = 1   AND Advert_Id = Id)
  AND Id in(SELECT Advert_id FROM AdvertsToAmenities WHERE Amenity_id = 3   AND Advert_Id = Id)
  AND Id in(SELECT Advert_id FROM AdvertsToAmenities WHERE Amenity_id = 5   AND Advert_Id = Id)  

-- OR --

SELECT TOP 50 Advert.Id
FROM Advert 
JOIN AdvertsToAmenities a on Advert.Id = a.Advert_id
JOIN AdvertsToAmenities b on Advert.Id = b.Advert_id
JOIN AdvertsToAmenities c on Advert.Id = c.Advert_id
WHERE a.Amenity_id = 1 
  AND b.Amenity_id = 3 
  AND c.Amenity_id = 5

I would love to find out how to optimize these queries!

Your queries look fine to me. Another alternative would be to use something like this:

SELECT TOP 50 Advert.Id
  FROM Advert JOIN AdvertsToAmenities a ON Advert.Id = a.Advert_id
 WHERE a.Amenity_id = 1 
    OR a.Amenity_id = 3 
    OR a.Amenity_id = 5
 GROUP BY Advert.Id
HAVING COUNT(DISTINCT a.Amenity_id) = 3

If the (Advert_Id, Amenity_id) pairs are unique, you can drop the DISTINCT.

How about the following restructure of your query which allows you to simply create a comma seperated list of specific amenity IDs?

SELECT TOP 50 
a.[ID]
FROM [Advert] a
INNER JOIN 
(
    SELECT ata.[Advert_ID]
    FROM [AdvertsToAmenities] ata
    WHERE ata.[Amenity_ID] 
    IN (1, 3, 4, 5) -- Your list of amenity IDs
) as ata
ON a.[ID] = ata.[Advert_ID]

This uses a dynamic table statement to prefilter only those applicable amenities before joining back against the list of adverts. Note, Sql Server will heavily optimise the sub query before execution. This should mean that you'll get the benefit of a more maintainable statement with all the optimisations that Sql Server provides.

* Try this simple *

SELECT TOP 50 a.Id
FROM Advert a, AdvertsToAmenities b 
WHERE a.Amenity_id in ('1','3','5')
and a.Id = b.Amenity_id