Re: LEFT JOIN not working

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Oops! I missed again.

If you specify conditions pertaining to the right-hand table, such as:
ads_clickrate.date = '2001',

Then you will lose all result rows for which the right-hand data is NULL.
Not the expected result.

So your restricting WHERE clauses must apply to the left-hand table only.

Therefore:
WHERE YEAR(ads_displayrate.date) = '2003' AND MONTH(ads_displayrate.date) =
'01'
(if your table ads_displayrate has such date fields).

HTH
Ignatius
____________________________________________
----- Original Message -----
From: "Lisi" <lists@shemeshdirectory.co.il>
To: "Ignatius Reilly" <ignatius.reilly@free.fr>
Sent: Thursday, January 09, 2003 6:54 PM
Subject: Re:  LEFT JOIN not working


> Cool! It's mostly working now, the only problem is it's ignoring the other
> clauses in the ON clause that select the desired date. Perhaps it's not
> supposed to be connected this way? How would I select specific dates?
>
> Thanks again,
>
> -Lisi
>
> At 01:20 PM 1/9/03 +0100, you wrote:
> >Oops! Sorry, I missed it the first time.
> >
> >Your query should start as:
> >SELECT ads_displayrate.name
> >instead of
> >SELECT ads_clickrate.name
> >
> >then you will always have a non-NULL name (coming from the table on the
left
> >of the LEFT JOIN).
> >
> >HTH
> >Ignatius, from Brussels
> >
> >"Where the fuck is Belgium?"
> >D. Ivester, CEO, Coca Cola
> >
> >____________________________________________
> >----- Original Message -----
> >From: "Lisi" <lists@shemeshdirectory.co.il>
> >To: "Ignatius Reilly" <ignatius.reilly@free.fr>; "PHP-DB"
> ><php-db@lists.php.net>
> >Sent: Thursday, January 09, 2003 1:11 PM
> >Subject: Re:  LEFT JOIN not working
> >
> >
> > > Exactly my question - why does it not have a name? How would I modify
my
> > > query to get a row with a name but null value for date? I thought the
join
> > > would take care of this, but I'm obviously not doing it right.
> > >
> > > You mention a unique identifier, there is a separate table with a row
for
> > > each ad, containing name, URL, and a unique ID number (autoincrement).
> > > Should this table be included somehow in the query? How would this
help?
> > >
> > > Thanks,
> > >
> > > -Lisi
> > >
> > > At 12:45 PM 1/9/03 +0100, Ignatius Reilly wrote:
> > > >Your 4th row ought to have an identifier of some sort. From your
SELECT
> > > >statement, this seems to be the name. Why does it not have a name?
> >Probably
> > > >what you want is a row with a name but a NULL value for
> >ads_clickrate.date.
> > > >
> > > >(by the way it is EXTREMELY advisable to use an abstract identifier,
such
> >as
> > > >an id, unique and required, instead of "name")
> > > >
> > > >Ignatius
> > > >____________________________________________
> > > >----- Original Message -----
> > > >From: "Lisi" <lists@shemeshdirectory.co.il>
> > > >To: "Ignatius Reilly" <ignatius.reilly@free.fr>; "PHP-DB"
> > > ><php-db@lists.php.net>
> > > >Sent: Thursday, January 09, 2003 12:18 PM
> > > >Subject: Re:  LEFT JOIN not working
> > > >
> > > >
> > > > > OK, this helped a bit.  Now I have, in addition to the three rows
of
> >ads
> > > > > that have ben clicked on, a fourth row with no ad name, 0
> >clickthroughs,
> > > > > and 24 displays. That plus the other three account for all the
> >displayed
> > > >ads.
> > > > >
> > > > > However, since it is returning a null value for any ad name that
has
> >not
> > > > > been clicked on, and then it's grouped by ad name, it lumps all
> > > >non-clicked
> > > > > ads into one row. What I need is to see each ad on a separate row,
> >which
> > > >is
> > > > > what I thought a LEFT JOIN was supposed to do.
> > > > >
> > > > > Any suggestions?
> > > > >
> > > > > Thanks,
> > > > >
> > > > > -Lisi
> > > > >
> > > > >
> > > > > At 11:07 AM 1/9/03 +0100, Ignatius Reilly wrote:
> > > > > >problem 1:
> > > > > >move the WHERE clauses to the ON clauses
> > > > > >
> > > > > >problem 2:
> > > > > >Obviously your intent with " COUNT(ads_clickrate.date) " is to
count
> >the
> > > > > >number of non-null occurences of click. But COUNT() is not the
> > > >appropriate
> > > > > >function to do this (it will simply give you the number of rows
> >inside a
> > > > > >group).
> > > > > >
> > > > > >Try replacing COUNT(ads_clickrate.date) by SUM( IF(
> >ads_clickrate.date IS
> > > > > >NULL, 0, 1 ) )
> > > > > >
> > > > > >HTH
> > > > > >Ignatius
> > > > > >____________________________________________
> > > > > >----- Original Message -----
> > > > > >From: "Lisi" <lists@shemeshdirectory.co.il>
> > > > > >To: "PHP-DB" <php-db@lists.php.net>
> > > > > >Sent: Thursday, January 09, 2003 10:44 AM
> > > > > >Subject:  LEFT JOIN not working
> > > > > >
> > > > > >
> > > > > > > I have a page with many ads that stores both the number of
times
> >an ad
> > > >is
> > > > > > > displayed and how many times it gets clicked.  These are
stored in
> >two
> > > > > > > different tables (since different information is stored for
each)
> >but
> > > >both
> > > > > > > have identical name columns. I am trying to display both #
times
> > > >displayed
> > > > > > > and # times clicked in the same table in an admin page.
> > > > > > >
> > > > > > > Here is my query:
> > > > > > >
> > > > > > > SELECT ads_clickrate.name, ads_clickrate.link,
> > > >SUM(ads_displayrate.count)
> > > > > > > as display, COUNT(ads_clickrate.date) as click FROM
> >ads_displayrate
> > > >LEFT
> > > > > > > JOIN ads_clickrate ON ads_displayrate.name =
ads_clickrate.name
> >WHERE
> > > > > > > YEAR(ads_clickrate.date) = '2003' AND
MONTH(ads_clickrate.date) =
> >'01'
> > > > > > > GROUP BY ads_clickrate.name ORDER BY ads_clickrate.name
> > > > > > >
> > > > > > > I want to display for each ad the number of times displayed,
and
> >then
> > > > > > > number of times clicked if applicable, if not 0.
> > > > > > >
> > > > > > > The query is only returning rows for ads that have been
clicked
> >on. Is
> > > >the
> > > > > > > problem because I have a COUNT column for one table, with a
group
> >by?
> > > >Is
> > > > > > > this causing the display to be grouped also?
> > > > > > >
> > > > > > > If you need more information how the table is set up let me
know,
> >I'm
> > > > > > > really stumped here.
> > > > > > >
> > > > > > > Thanks,
> > > > > > >
> > > > > > > -Lisi
> > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > PHP Database Mailing List (http://www.php.net/)
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> > > > > > >
> > > > > > >
> > > > >
> > > > >
> > > > > --
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> > > > >
> > > > >
> > >
> > >
>
>


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