Hi guyst.. thanks for the replies, really, them make me suppose that all what i've learned of sql from mysql can be wrong.. But still i have some trouble to understand the functionality of the orders example. My first goal is to retrieve every order, the customer name, and the total of the idems per order.. so (from my point of view) i *dont* need and *dont* ant to group by the costumer name, becose every costumer can have many orders... and, as i understand the query: --- SELECT orders.code, customer.name, SUM(order_item.price) FROM orders INNER JOIN customer ON (customer.id = orders.id_customer) INNER JOIN order_item ON (order_item.id_order = orders.id) GROUP BY orders.id, customer.name --- it *try* to group by the customer name, but *fail* becose the GROUP priority is at the order's code.. how much am i far from it? but aswell i cant understand why i must group for the costumer name, when i dont want and dont need it to be *unique* So, lets suppose that i want to retrieve the total price of every item bought by every customer, i'll start with this query: --- SELECT customer.name, SUM(order_item.price) FROM customer INNER JOIN orders ON (orders.id_customer = customer.id) INNER JOIN order_item ON (order_item.id_order = orders.id) GROUP BY customer.id --- but still, SQL throw an error, and i must add the costumer.name in the group clause. And still, that will be *ignored* becose the *main* GROUP BY is customer.id.. and the query works. So, suppose i have thosa data: customer id | name 1 | Abigail 2 | Steve orders: id | id_customer | code 1 | 1 | 0001 2 | 2 | 0002 3 | 1 | 0003 order_item: id | id_order | price | 1 | 1 | 21.23 | 2 | 1 | 21.32 | 3 | 2 | 21.23 | 4 | 2 | 21.32 | 5 | 3 | 21.23 | 6 | 3 | 21.32 | So, Abigail have 2 orders, steve 1, every order have 2 items. If i would to retrieve the number of orders, the number of total items bought (total sum of every order) for every customer, the query shuold be like that: --- SELECT customer.name, COUNT(orders.id), ( SELECT COUNT(order_item.id) FROM orders INNER JOIN order_item ON (order_item.id_order = orders.id) WHERE orders.id_customer = customer.id GROUP BY orders.id_customer ) AS total_items FROM customer INNER JOIN orders ON (orders.id_customer = customer.id) GROUP BY customer.id, customer.name --- Right? -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
