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Posted by Shelly on 11/11/07 01:53
ZeldorBlat wrote:
> On Nov 10, 8:29 pm, "Shelly" <sheldonlg.n...@asap-consult.com> wrote:
>> I know [Jerry and co.] that this is off-topic, but the sql group
>> that I could find online doesn't have much traffic, so here goes.
>>
>> I cam across this code:
>>
>> SELECT AnnoID, AnnoTitle,
>> (SELECT EventTitle FROM mEVENTS WHERE tblANNOUNCE.AnnoLink =
>> mEVENTS.EventID)
>> as AnnoLink,
>> date_format(AnnoDate,'%M %D %Y') as date
>> FROM tblANNOUNCE
>> ORDER BY AnnoDate DESC, AnnoLink, AnnoTitle
>>
>> I am having trouble reading this. Is this the same as:
>>
>> SELECT a.AnnoID, AnnoTitle, e.EventTitle as AnnoLink,
>> date_format(AnnoDate,'%M %D %Y') as date
>> FROM tblANNOUNCE AS a, mEVENTS AS e
>> WHERE a.AnnoLink = e,EventID
>> ORDER BY date DESC, AnnoLink, AnnoTitle
>>
>> In other words, do they do exactly the same thing? I can't get the
>> former to run on the current version of MySQL. Apparantly (I was
>> told) it ran on a later version of MySQL.
>>
>
> They should be the same. I generally see the first type of query when
> someone doesn't really understand joins. It also typically results in
> horrible performance.
Hmmm. I learned the second type about 25 years ago and is always how I do
those joins. My client's customer changed servers and the new server has an
older version of MySQL. They ran into problems with many queries. I
started looking at the code, and the first one I came accross was the first
version (longer in length, I stripped it down for the posting). I copied
that code and went to phpmyadmin and did a sql query. It barfed and
complained mightily on the sub-select. I tried to analyze what the original
coder was intending to do, and came up with the second one (I wrote that
one). That one worked. I just wanted some verification from other
professionals that I was reading the original correctly in what the coder
was intending to do -- before I proceeded on my merry way modifying code in
some twenty modules.
--
Shelly
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