group by - SQL MAX returns multiple values but I only want the MAX value

Question

I am relatively new to SQL. So I am doing an excersise in which they ask me to select the most expensive product for every maker, and the output should have maker, model, and price.

I succesfully created a query that gives all models and prices for each maker,the query is as follows:

SELECT MODEL, MAKER, PRICE 
  FROM PC 
 INNER JOIN(SELECT MAKER, MODEL 
              FROM PRODUCT 
             WHERE MAKER='Dell') 
 USING (MODEL);

And what it throws is this:

MODEL	MAKER	PRICE
d1	Dell	500
d2	Dell	600
d3	Dell	700
da	Dell	800
dzero	Dell	1200

question from:https://stackoverflow.com/questions/65640875/sql-max-returns-multiple-values-but-i-only-want-the-max-value

Answer 1

You can use DENSE_RANK() function, if your database is eligible to use window functions such as

SELECT model, maker, price
  FROM(SELECT pc.model, pc.maker, pc.price,
              DENSE_RANK() OVER (PARTITION BY pc.maker ORDER BY pc.price DESC) AS dr
         FROM pc  
         JOIN product pr
           ON pr.model = pc.model 
          AND pr.maker = 'Dell' ) p
  WHERE dr = 1