(INNER table predicate in where-clause vs ON-clause is well covered online and also in my own http://bigblog.tanbin.com/2011/05/whats-different-between-these-2-sqls.html)
Note intermediate table is unaffected by where-clause. Query processor always uses on-clause exclusively to build an intermediate joined table before applying where-clause. This is the logical view we can safely assume. Physically, Query processor could optimize away the where/on distinction, but output is always consistent with the logical view.
Q1: can we _always_ assume that LL-outerjoin-RR intermediate table _always_ includes all LL rows if no outer table predicate in ON-clause?
A: yes with the big “if”
%%A: If you need to filter on outer table, do it in where-clause — better understood. Avoid ON-clause.
Q2: Boldly dropping the big “if”, can we _always_ assume that LL-outerjoin-RR intermediate table _always_ includes all LL rows _regardless_ of outer table predicate in ON-clause?
%%A: probably yes.
If you really really want outer table predicate in ON-clause, I assume you have no good reason and just feels adventurous.
http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc32300.1502/html/sqlug/sqlug169.htm shows that even with outer table predicate in ON-clause, we still get “… all LL rows”
select title, titles.title_id, price, au_id
from titles left join titleauthor
on titles.title_id = titleauthor.title_id
and titles.price > $20.00
title title_id price au_id
-------------------- --------- ------ ---------------
The Busy Executive’s BU1032 19.99 NULL
Cooking with Compute BU1111 11.95 NULL
You Can Combat Compu BU2075 2.99 NULL
Straight Talk About BU7832 19.99 NULL
Silicon Valley Gastro MC2222 19.99 NULL
The Gourmet Microwave MC3021 2.99 NULL
The Psychology of Com MC3026 NULL NULL
But Is It User Friend PC1035 22.95 238-95-7766
