RE: next baby step in SQL: start using join

Dan,

As always, it depends.  YMMV.  Use what works for you. 

I'll make a few points and you can decide as you like.

Letting the optimizer make the chioce is not always the best plan.  The
optimizer is often set to timeout after a period of time if it hasn't yet
finished its analysis.  The engine then proceeds with the current best
choice, regardless of other "better" methods.  

Opinion: I like the formal syntax because you are distinctly telling the
optimizer what you intend.  I believe the optimizer can discard many of the
evaluations it might have to do with a simple join statement. 



Eric DeLong
Sally Beauty Company
MIS-Project Manager (BSG)
940-898-7863 or ext. 1863



-----Original Message-----
From: Dan [mailto:dbcemid@xxxxxxxxx]
Sent: Friday, March 28, 2003 9:21 AM
To: Midrange Systems Technical Discussion
Subject: Re: next baby step in SQL: start using join


Ok, guys, I'm seeing two schools of thought here.  Dave & Gord say to let
the WHERE do the
"joining", whereas Rick suggests using JOIN and taking care of file
placement in the join.

Gord also mentions that using WHERE will cause the query optimizer to
determine the best path.

I spruced up Rick's example and came up with:
 Select  All     T01.JOBNUM, T01.REVNUM, T01.PHSCD,
                   T01.CCPNUM, T01.CCPAMT, T02.CSTTYP 
  From           PCPESTCCP T01           
            join PCPJOBHDR T03 on        
                  T01.JOBNUM = T03.JOBNUM
            join PCPTBLCCP T02 on        
                  T03.CMPNUM = T02.CMPNUM
              and T01.CCPTYP = T02.TBLID 
              and T01.CCPNUM = T02.CCPNUM
  Where         T01.JOBNUM = '3ACM0170'
            and T02.CSTTYP = 'C'

I suppose it gets into personal opinion, but, in this example anyway, I find
using the JOIN makes
it more apparent that you are joining files and how you are joining them.
(vs. using WHERE to do
the join.)

Comments and advice are welcome & appreciated.

- Dan

--- "Smith, Dave" <DSmith@xxxxxxxxx> wrote:
> Dan:
>  
> The join using the WHERE is no different than the join using the JOIN. (A
rose by any other
> name....)  Within my embedded SQL, I like to use the JOIN operator because
it's consistent with
> the LEFT OUTER JOIN and EXCEPTION JOIN operators.   I must say the more
SQL I learn, the more I
> love it!
>  
> David Smith
> dsmith@xxxxxxxxx  

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