I haven't tried the union method.... the query i have is actually
quite a bit more complicated than just a simple select * from a
single table, so while it may work, it might take a while to write it
if I am reading all this right.
But yes, the ifnull() method works just fine. Thanks for your help.
--
Kevin Murphy
Webmaster: Information and Marketing Services
Western Nevada Community College
www.wncc.edu
775-445-3326
On Dec 21, 2006, at 10:12 AM, <tg-php@xxxxxxxxxxxxxxxxxxxxxx> <tg-
php@xxxxxxxxxxxxxxxxxxxxxx> wrote:
You shouldn't have to do that. the IFNULL() handles all that. If
the item is null, it returns an emptry string ''. If it's blank/
empty, it returns an empty string. This is just used for the
comparison = ''. This determines if it's empty or null and if so,
returns 'ZZZZZZZZZZZZZZZZZZZZZZZZZZ', if not, it returns the
unaltered value. And again, this returned value is only used for
the sorting. The values you get from "select *" will be unaltered.
Is this more efficient than doing two SELECTs and a UNION? I have
no idea. But I like to keep things as clean as possible and in my
reading and experience, letting the server handle an IFNULL()
function should be quicker than doing four value checks (is null,
is not null, = '' and != ''), collecting the values of two SELECTS
then checking to see if it's able to UNION them together.
Also, less code/typing typically means less chance of typos.
BTW: In my example, realistically you could probably shorten the
morphed value to "ZZ" or "ZZZ" unless you think you'll values in
your database that will start with "ZZZZ" and get bumped lower on
the sorting.
-TG
= = = Original message = = =
In case the blank is a null or is really a blank:
select * from blank where tchar_10 is not null and tchar_10 != ''
union all
select * from blank where tchar_10 is null or tchar_10 = ''
- Dave
On 12/21/06, tg-php@xxxxxxxxxxxxxxxxxxxxxx <tg-
php@xxxxxxxxxxxxxxxxxxxxxx>
wrote:
This is a little weird looking, but should do the job. Remember that
items in your 'order by' can be manipulated conditionally. In
this case,
I'm looking for NULL as well as '' (empty) and changing it to
something that
should come after all your normal alphabetical values, but it
doesn't change
what appears in your results. This only affects the sorting:
select * from sometable order by if(ifnull(somecolumn, '') = '',
'ZZZZZZZZZZZZZZZZZZZZZZZZ', somecolumn)
Hope that helps.
-TG
= = = Original message = = =
I have this column in mysql:
A
F
D
[ empty ]
A
C
If I do an order by on that column, this is what I get:
[ empty ]
A
A
C
D
F
What I would like is this:
A
A
C
D
F
[ empty ]
Is there any way to achieve this in a single MySQL query? Using DESC
in this case doesn't work, because while it puts the empty row in the
last place, it does the rest as well. I could also do 2 queries where
it calls it once in order WHERE !='', and then do another query to
get the empty ones, but that seems a bit cumbersome.
--
Kevin Murphy
Webmaster: Information and Marketing Services
Western Nevada Community College
www.wncc.edu
775-445-3326
--
Kevin Murphy
Webmaster: Information and Marketing Services
Western Nevada Community College
www.wncc.edu
775-445-3326
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