SQL question

[makhlo]

Hey everybody,

I am new to sql and have a problem to find the solution for this exercise: Find out the makers that sale PCs but not laptops.

The database scheme consists of four relations:

Product(maker, model, type)
PC(code, model, speed, ram, hd, cd, price)
Laptop(code, model, speed, ram, hd, screen, price)
Printer(code, model, color, type, price)

My own query:

select distinct maker from product, pc
where product.model = pc.model
and type in('pc','printer')

The problem is that i also get the makers who sells pc and laptops.

Thnx for any help,

[jasonahoule]

Try this:

SELECT DISTINCT maker
FROM product
WHERE product.model IN
(SELECT pc.model
FROM pc);

[makhlo]

I tried the query you made:

SELECT DISTINCT maker
FROM product
WHERE product.model IN
(SELECT pc.model
FROM pc);

but still get the makers who sell pc and laptops. there must be a solution to filter this makers.

Thnx for you're reply

[jasonahoule]

Sorry, misunderstood what you were saying. Try something like this:

SELECT DISTINCT maker
FROM product
WHERE maker NOT IN
(SELECT maker
FROM product, laptop, printer
WHERE product.model = laptop.model
AND product.model = printer.model);