How do you join three tables in Oracle? [closed] - sql

Question

Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.
This question appears to be off-topic because it lacks sufficient information to diagnose the problem. Describe your problem in more detail or include a minimal example in the question itself.
Closed 9 years ago.
Improve this question
I'm having a hard time joining three separate tables in Oracle. I'm never joined three tables before so I'm not well versed. My theory is below:
SELECT customer_num WHEN customer_num IS 104 -198, order_num
FROM orders INNER JOIN items
ON order_num, stock_num
INNER JOIN stock
ON stock_num, description
Essentially, I'm trying to start with the ORDERS table and pull the customer number (customer_num) specifically customer number 104 -108 and the order_num from the orders table. Then attach the orders table to the Items table and attach the order_num and stock_num, and lastly attach the stock table and pull out the stock_num and description.

Answer 1

Your syntax is all over the place, and wouldn't work for a two-table join, or even querying a single table. Not sure where you got WHEN from, or the order of your clauses. Please review the SQL reference to see how to join and how to filter. Anyway...
You seem to want something like this:
SELECT o.customer_num, o.order_num, i.stock_num, s.description
FROM orders o
INNER JOIN items i ON i.order_num = o.order_num
INNER JOIN stock s ON s.stock_num = i.stock_num
WHERE o.customer_num BETWEEN 104 AND 198;
The WHERE clause is being applied to the orders table to restrict which customers' orders you get. I've assumed from your description that the orders and items tables have a common order_num column you can join on; and that the items and stock tables have a common stock_num column you can join on.
As OldProgrammer said, it would be helpful to include your table schemas in the question so assumptions don't need to be made, and showing sample data and expected output for that data would clarify what you're trying to do.

Answer 2

It should look something like this (based on the limited information about the schema)...
SELECT
O.CUSTOMER_NUM,
O.ORDER_NUM,
S.STOCK_NUM,
S.DESCRIPTION
FROM
ORDERS O,
ITEMS I,
STOCK S
WHERE
I.CUSTOMER_NUM >= 104
AND I.CUSTOMER_NUM <= 198
AND O.ORDER_NUM = I.ORDER_NUM
AND I.STOCK_NUM = S.STOCK_NUM

Answer 3

The syntax for a JOIN is:
TableExpression [ INNER ] JOIN TableExpression
{
ON booleanExpression | USING clause
}
The booleanExpression is what the tables will be linked by. So, in your example, something like this:
SELECT customer_num WHEN customer_num IS 104 -198, order_num
FROM orders INNER JOIN items
ON orders.<some_column> = items.<some_column>
INNER JOIN stock
ON items.<some_column> = stock.<some_column>