i’m experting a lot of from you.

thanks and regards, murugan

Yes, why not. If the OUTER JOIN implicitly means LEFT OUTER JOIN, that should work, making LEFT/RIGHT optional.

My guess is the committee argued over it

That is a plausible guess.

I can’t see why they needed either of them. Why not just “OUTER JOIN”? My guess is the committee argued over it for a week and finally agreed to include everyone’s suggestions just so they could get on with something else, like recursive subquery factoring or the MODEL clause.

FROM customers LEFT OUTER JOIN orders

is the same as:

FROM orders RIGHT OUTER JOIN customers 

You can always stick with LEFT (or RIGHT) and just switch table positions based on your requirement. I have no idea why both keywords are needed, maybe it just made sense that every right had a left and every left had a right.

Say you want to list customers and their orders, and you want to include customers who not have placed an order, so your query is an outer join driven from CUSTOMERS. Your FROM clause would intuitively (at least, to me) start with CUSTOMERS:

FROM customers LEFT OUTER JOIN orders

Surely it is ORDERS that is being joined? And it’s on the right? And if you wanted the join the other way around wouldn’t you just write

FROM orders LEFT OUTER JOIN customers

rather than writing it backwards and switching to “RIGHT OUTER JOIN” syntax? Why did they even need to invent two syntax options for exactly the same thing anyway? (I suspect this was a committee decision.)

While I’m at it, I would always begin any ORDERS predicate with a column name from ORDERS, e.g:

FROM customers c LEFT OUTER JOIN orders o ON o.order_id = c.order_id

(notice that “o” is now on the left) for the same reason that I would write

WHERE ename = ‘FORD’

and not

WHERE ‘FORD’ = ename

Bafflingly (to me), I often see it written backwards.

btw the interaction of WHERE clauses with outer joins might be worth a mention, as it seems to be another source of confusion.