Find all PC’s makers which doesn’t produce laptops

–Find all PC’s makers which doesn’t produce laptops
 
1. SELECT DISTINCT maker
FROM product WHERE
maker NOT IN (SELECT maker FROM product WHERE type =
‘LAPTOP’)
AND type = ‘PC’
 
2. SELECT DISTINCT p1.maker
FROM         product AS p1 LEFT OUTER JOIN
                      product AS p2 ON p1.maker = p2.maker AND p2.type =
‘Laptop’
WHERE     (p1.type = ‘PC’) AND (p2.maker IS NULL)

1. Find models and prices of all products manufacured by ‘B’

Find models and prices of all products manufacured by ‘B’. There are two ways to get this data:
 
1. SELECT DISTINCT product.model, COALESCE (laptop.price, pc.price, printer.price, 0) AS Expr1
FROM         product LEFT OUTER JOIN
                      laptop ON laptop.model = product.model LEFT OUTER JOIN
                      pc ON pc.model = product.model LEFT OUTER JOIN
                      printer ON printer.model = product.model
WHERE     (product.maker = ‘B’)
 
 
2. SELECT     product.model, type.price
FROM         product INNER JOIN
                          (SELECT     model, price
                            FROM          laptop
                            UNION
                            SELECT     model, price
                            FROM         pc
                            UNION
                            SELECT     model, price
                            FROM         printer) AS type ON product.model = type.model
WHERE     (product.maker = ‘B’)