Ordering Database Records

Question

Hi all, thanks for reading...
I have table with some simple columns and rows in it. I
wanted to have full control over the order these elements appeared
so created a column named "item_order" which holds a number (1
being highest priority) for each record.
The table looks something like this...(cutting off irrelivant
columns)
ITEM_ID ITEM_ORDER ITEM_PARENT_ID
2 1 1
8 2 1
9 3 1
Numbers not to be read as 211 for example but rather a number
for each column (sorry about the formatting!)
What I basically need to do is design some kind of way that I
can change these orders dynamically with a query.
For example, if i loop through all these records here, each
would be linked and have four options as follows...
Top, Up, Down, Bottom
Top would set the item_order of the selected link in the
output loop to 1 and the rest would have to shift - the same idea
would work for Bottom except giving it the highest number and
shifting the other records the other way (im not worrying about up
and down just yet).
Example output...
<cfoutput query="my_query">
#item_title#
<a
href="index.cfm?item_id=#item_id#&position=top">Top</a>
<a
href="index.cfm?item_id=#item_id#&position=up">Up</a>
<a
href="index.cfm?item_id=#item_id#&position=down">Down</a>
<a
href="index.cfm?item_id=#item_id#&position=bottom">Bottom</a>
</cfoutput>
Each different action would call a different function (cfc)
with a query in it which will do all the necessary stuff to modify
the item_order column depending on the item_id and shift all other
records item_orders accordingly.
I have had a go - please see code attached....and while this
works sometimes and it doesn't throw an error it has
inconsistencies and is a little buggy.
I'm pretty sure this shouldn't be that hard but i'm finding
it very tricky.
Any help or advice would be greatly appreciated. If you don't
understand what I mean or I am being a little confusing please
clarify with me and I'll try again.
Many thanks,
Michael.
PS - This is all so I can then have the desired effect of
explicitly ordering my items for display. Take the following query
for example...
<cfquery name="items" datasource="#request.dsn#"
username="#request.username#" password="#request.password#">
SELECT *
FROM ob_items
WHERE item_parent_id = <cfqueryparam
value="#arguments.item_id#" cfsqltype="cf_sql_integer" />
AND item_deleted = 'No'
ORDER BY item_order ASC
</cfquery>
This would order by the item_order column where my items will
be 1,2,3,4 etc.

Answer 1

Hi,
Thanks for the response, it's nice to get another view from
someone outside of my own head!
I'm a bit confused about this line though in the first
query...
WHERE item_id <> #chosen_item#
In theory, if I am correct, this query will update all the
rows item_order column to the value it currently is + 1 where the
ID is less than or greater than the chosen items ID. But this
doesn't make sense if the only items that need to be modified in
the TOP function are items with the item_order column value less
than the selected items item_order value. Am I making any sense?
E.g. If I have items with orders of 1,2,3,4 and I want to
move the row with item_order 3 to the top then the record with
value of three will need its item order updating to 1 and any items
above it (1 and 2) need to shift up one so 1 becomes 2 and 2
becomes 3....replacing the original 3rd position. So record with
the item_order of 4 in this case isn't touched at all because
moving an item to the top which was already above it should not
affect it.
If you have the time to explain it a little more I'd be
really greatful...I am even surprised someone managed to decipher
what I even said!
Many thanks,
Mikey.