Question

I have 4 tables. Im trying to get the max value for each car brand. There are 10 BRANDS. Im trying to get which car is the most expensive for each brand.

The first thing i did was group all the tables from where I wanted to get information.
I’ve join tables BRAND, MODEL, CLASS, AND VEH. I’m not really sure how to get the max for each group however.

SELECT B.BRAND_NAME, M.MODEL_NAME, C.CLASS_NAME, V.VEH_YEAR,  V.VEH_PRICE

FROM ((VEHICLE V INNER JOIN CLASS C ON V.CLASS_ID = C.CLASS_ID)
INNER JOIN MODEL M ON M.MODEL_ID = V.MODEL_ID)
INNER JOIN BRAND B ON B.BRAND_ID = M.BRAND_ID

I tried:

SELECT B.BRAND_NAME, M.MODEL_NAME, C.CLASS_NAME, V.VEH_YEAR,  V.VEH_PRICE
FROM (
SELECT B.BRAND_NAME, MAX(V.VEH_PRICE)
FROM ((VEHICLE V INNER JOIN CLASS C ON V.CLASS_ID = C.CLASS_ID)
INNER JOIN MODEL M ON M.MODEL_ID = V.MODEL_ID)
INNER JOIN BRAND B ON B.BRAND_ID = M.BRAND_ID
GROUP BY B.BRAND_NAME
);

Im getting:

Answer 1

Your joining would be fine if you wanted only the maximum vehicle price per brand. It would need only a GROUP BY and the MAX() function (notice that you don’t need the Class table for this):

SELECT B.BRAND_NAME, 
       MAX(V.VEH_PRICE) AS MAX_VEH_PRICE

FROM ( VEHICLE V
  INNER JOIN MODEL M ON M.MODEL_ID = V.MODEL_ID )
  INNER JOIN BRAND B ON B.BRAND_ID = M.BRAND_ID

GROUP BY B.BRAND_ID, B.BRAND_NAME ;

To get all the vehicles’ data for those vehicles that have the maximum price, you need to write the previous query in a subquery ( a derived table) and then join again:

SELECT B.BRAND_NAME, M.MODEL_NAME, C.CLASS_NAME, V.VEH_YEAR,  V.VEH_PRICE

FROM  
    ( ((VEHICLE V INNER JOIN CLASS C ON V.CLASS_ID = C.CLASS_ID)
      INNER JOIN MODEL M ON M.MODEL_ID = V.MODEL_ID)
      INNER JOIN BRAND B ON B.BRAND_ID = M.BRAND_ID
    )

  INNER JOIN

    ( SELECT M.BRAND_ID, 
             MAX(V.VEH_PRICE) AS VEH_PRICE  
      FROM (VEHICLE V
        INNER JOIN MODEL M ON M.MODEL_ID = V.MODEL_ID)
      GROUP BY M.BRAND_ID 
    ) AS derived

    ON  b.BRAND_ID = derived.BRAND_ID
    AND v.VEH_PRICE = derived.VEH_PRICE ;