Question

I’m trying to outer join a table onto two others tables referenceing them both to the joined table. For example:

table1 = order_header
table2 = order_line
table3 = inventory

So i need to get specific orders so i need to look at order_header and order_line and also want to retrieve the inventory records which might no exist (which is where i think to outer join in). The problem is, the only way i can see if inventory exists is looking at both the order_header and and order_line to match to the inventory.

order_header.location = inventory.location
order_line.product = inventory.product

But i can outer join inventory referenceing both the order_header and order_line detail?

Sorry for the poor explanation but any help would be appreciated.

Thanks.

Gillian.

Answer 1

Try this :

SELECT * FROM order_header
INNER JOIN order_line ON order_header.header_id = order_line.header_id
LEFT OUTER JOIN inventory ON order_line.product = inventory.product AND order_header.location = inventory.location
WHERE order_header.header_id = xxx

It works because the first inner join between order_header and order_line can then be considered as one single table, so you just left join on that – kind of fictive – table