"Why don't you simply convert these queries to ordinary JOINs?"
...because we've already got a 90% finished application (75 tables/150 jsp
pages).
I was toying around with the idea last night of using a JOIN instead of
EXISTS but i'd have to change the way the persistence layer works. I'm not
sure that it's a good idea to use joins (often requiring the DISTINCT
clause) instead of EXISTS -- seems like a "tail wagging the dog" strategy.
Isn't EXISTS a lot more efficient than an inner join?
We're going to offering the application on Oracle and so I wouldn't like to
de-optimize the SQL just so it works on mysql 4.0 if 4.1 will be out within
a few months.
Seems like I might be best to check again in a while and see how quickly you
guys have progressed with 4.1.
Cheers,
Greg.
----- Original Message -----
From: "Harald Fuchs" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, November 10, 2002 11:16 PM
Subject: Re: MySql 4.1 Sub Selects
> In article <014701c288a4$1b1bb550$0100a8c0@dev>,
> "Greg Matthews" <[EMAIL PROTECTED]> writes:
>
> > Your call. If a 4.1 binary was available then I'd spend time testing it
with
> > a J2EE app under JBoss on Windows XP -- otherwise i'll just have to
wait.
>
> > 95% of the subselects I do are simple correlated subqueries like this:
>
> > select <columns>
> > from tableA
> > where exists (
> > select 1
> > from tableB
> > where tableB.myCol = tableA.myCol
> > )
>
> > or
>
> > select <columns> from tableA
> > where exists (
> > select 1
> > from tableB
> > where tableB.myCol = tableA.myCol
> > and tableB.someCol in ('A','B','C')
> > )
>
> Why don't you simply convert these queries to ordinary JOINs?
> Me thinks that's easier than experimenting with unoptimized pre-alpha
> code.
>
> [Filter fodder: SQL query]
>
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