I would think you would want to use the EXISTS operator for the reason you
specified - portability - as well as I believe that vendors often optimize
it somewhat for performance.
Cheers
-----Original Message-----
From: Dain Sundstrom [mailto:[EMAIL PROTECTED]]
Sent: Friday, August 17, 2001 4:32 PM
To: [EMAIL PROTECTED]
Subject: Re: [JBoss-dev] JDBC SQL Extensions
Sorry for the confusion. There are two issues here.
==================================================
Issue1: use of the {fn concat(str1, str2)} style functions.
Solution: use fn style functions as default but have override in xml like:
<concat-function>CONCAT (?1, ?2)</concat-function>
or some thing simmilar.
==================================================
Issue 2: IS EMPTY function. How should I map the following ejb-ql query:
SELECT OBJECT(o)
FROM Order o
WHERE o.lineItems IS EMPTY
Solution A:
SELECT o.ordernumber
FROM Order o
WHERE NOT EXISTS (
SELECT l.pk
FROM Order o, LineItem l
WHERE o.ordernumber = l.ordernumber)
I like this because it does not use an outer join (thanks Dave Smith). Does
it have performance problems?
Solution B:
SELECT o.ordernumber
FROM Order o LEFT OUTER JOIN LineItem l ON o.ordernumber = l.ordernumber
WHERE l.ordernumber IS NULL
This would be a major pain to map to all vendors.
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