Hiya!
I have a question:
I have 2 tables... "Inventory" and "Price"
These tables are used by 2 restaurants... the inventory has what they sell,
and prices has the corresponding prices to those items for each location.
What I want to do:
I want to get a list of all items in the "Inventory" table and the
corresponding price from the "Price" table for a location, unless the column
"SHOW" (in the "Price" table) is set to "N"
It might sound like "Just use a LEFT JOIN"... but if there is no entry for
the item in the "Price" table, I still want a result
I tried using:
===============
select i.name, p.price1
from inventory i
LEFT JOIN prices p
ON p.itemID=i.itemID
where (
(i.itemType=7)
AND (i.canusa='usa')
AND (p.storeID=99)
AND (p.show='y')
)
===============
But that only returns the items that have prices set up in the prices
table...
So I tried adding
===============
OR (NOT EXISTS (SELECT * FROM prices where (p.itemID=i.itemID) AND
(i.itemType=7))
)
===============
to the end of the WHERE conditions, but this returns everything in the
inventory table
I then tried changing the whole statement to:
===============
select i.name, p.price1
from inventory i
LEFT JOIN prices p
ON p.itemID=i.itemID
where (
(i.itemType=7)
AND (i.canusa='usa')
AND (p.storeID=99)
AND (p.show='y')
)
OR (i.itemType=7)
AND (i.canusa='usa')
AND (NOT EXISTS (SELECT * FROM prices where (p.itemID=i.itemID) AND
(i.itemType=7)))
===============
Now that does work... BUT, I am repeating some of the conditions of the
WHERE statement: (i.itemType=7) AND (i.canusa='usa')
And I am wondering if this is the most efficient way of doing it, or if its
just some bandaid approach that works and the true logic has escaped me?
(and is the "not exists" condition going to give some extra load the server
or not)
Any help is appreciated
Thanks,
Clint
