SQL, select in tables - sql

Question

Hey I don't know how to do it....
Its a homework: List the code and the consumers who bought cars only 'Argentina' country.
Table sell:
customer | resell | veicle | date | value
---------+---------+-----------+------------+----------
02 | 01 | 03 | 2010-02-05 | 17500.00
04 | 02 | 01 | 2010-01-07 | 28000.00
01 | 03 | 08 | 2010-02-15 | 28000.00
02 | 03 | 02 | 2010-03-12 | 42000.00
03 | 04 | 06 | 2010-02-06 | 11500.00
03 | 02 | 05 | 2010-01-25 | 22100.00
01 | 01 | 04 | 2010-01-21 | 15500.00
Table customer:
cod | name | lastname
--------+------------+------------
01 | Jose | Alves
02 | Paulo | Cunha
03 | Maria | DPaula
04 | Joana | Silveria
Table veicle:
cod |manufacturer| model | year | country | price
--------+------------+-----------------+------+-----------+----------
01 | 01 | Gol | 2000 | Brasil | 25000.00
02 | 01 | Golf | 2005 | Argentina | 39000.00
03 | 04 | Ford Ka | 1990 | Brasil | 15000.00
04 | 03 | Corsa Seda | 1995 | Brasil | 12500.00
05 | 04 | Fiesta | 2003 | Argentina | 20000.00
06 | 03 | Corsa Seda | 1995 | Argentina | 10000.00
07 | 05 | Palio | 2002 | Brasil | 15000.00
08 | 05 | Siena | 2006 | Brasil | 26000.00
I guess it to start:
SELECT customer.cod, customer.name
FROM sell, customer
WHERE (SELECT cod
FROM veicle
WHERE veicle.country = 'Argentina') = sell.veicle;
To select only the argentine cars...
Please guide-me to the answer.

Answer 1

SELECT c.*
FROM customer c
WHERE EXISTS (
SELECT 1
FROM sell s
JOIN veicle v ON v.cod = s.veicle
WHERE s.customer = c.cod
AND v.country = 'Argentina'
)
AND NOT EXISTS (
SELECT 1
FROM ...
);
I'll leave the rest for you, as this is homework. Fill in for ... to exclude customers that have bought vehicles that are not from Argentina - very similar to the first EXISTS clause. If you have understood the first, you can complete the rest.

Answer 2

Try this
SELECT DISTINCT customer.cod, customer.name || customer.lastname FROM customer, veicle, sell WHERE customer.cod = sell.customer AND veicle.cod = sell.veicle AND veicle.country = 'Argentina'

Answer 3

Look into table joins. That way instead of doing a subquery (what is in your where statement) you can instead join on the tables (kindof like your From clause but you should specify what it joins on) and then in your where you can just put veicle.country = 'Argentina'.
And FYI veicle is spelled wrong. It should be vehicle.

Answer 4

Try this :
SELECT c.cod, c.name,c.last_name,v.model
FROM sell as s JOIN customer as c JOIN veicle as v ON s.veicle = v.cod and s.customer = c.cod
WHERE v.country = 'Argentina'

Answer 5

WITH minima AS (
SELECT DISTINCT s.customer
, MIN(v.country) AS mi
, MAX(v.country) AS ma
FROM sell s
JOIN veicle v ON s.resell = v.cod
GROUP BY s.customer
)
SELECT cu.* FROM customer cu
JOIN minima mm ON mm.customer = cu.cod
WHERE mm.mi = 'Argentina'
AND mm.ma = 'Argentina'
;