Any linked children?

[Tom Cone Jr]

Assuming a two table set, say Ord_hdr as parent, linked 1:N to Ord_items. Assume further the set supports a form.

What's the fastest way to determine if any given parent record has at least one child record linked to it?

I am using the exist() function and it works well. Is there a faster way?

Context: I'm working on the onchange event script in a field in the hdr table. When it fires I want my onChange script to determine if there are any linked child records. I don't need to know the number of linked records, just whether or not ANY are linked.

Is there something faster than Exist()?

Thanks.

-- tom

[Clunes]

Re: Any linked children?

What about a5_get_records_in_query()? Probably same speed

[Ted Giles]

Re: Any linked children?

Sorry to be a bit dim here Tom, but if the OnChange is running from the Header Record in the Form, would it not be easier to have a Variable set - and use that value - if there is linked data using OnFetch, or a Calculated Field which could be used? Then the normal process of fetching a record will tell you if there is a linked record.
I might have missed the point here if you want to find any links at all in the set no matter which record you were looking at, but I took it that the link was specific to the Order.

[Tom Cone Jr]

Re: Any linked children?

Mark, actually I thought of that but believe it to be slower. Has to open the table run a query and get a count. I don't need a count. An indexed find by key (like the exist() function uses) is faster. I'm just wondering if there's something I can do that will save me from having to open another instance of the child table. Thanks anyway. -- tom

[Tom Cone Jr]

Re: Any linked children?

Ted, thanks for the idea. Had not thought of that. Two questions for you: (a) what expression or function would you use in the OnFetch event to determine if there is a linked child record? (b) Do I really want this extra processing to occur on each fetch, or do I simply want to pay the performance penalty only when the field values changes?

[Corelius]

Re: Any linked children?

May be you are looking for the function hasChildRecords()

http://wiki.alphasoftware.com/haschi...rds%20Function

Cornelius

[Tom Cone Jr]

Re: Any linked children?

Thanks, Cornelius. Thought maybe something like that was available, but could NOT find it using the Wiki.

Will now see if I can determine whether it's faster than exist() or not.

-- tom

[Ted Giles]

Re: Any linked children?

Tom, how important is performance in this app?
As far as the OnFetch event is concerned, I was thinking of something very simple like [if (field in child table="" or Null)] then there is no actual link at that point.

[Tom Cone Jr]

Re: Any linked children?

Ted, that's interesting, too. Haven't tried it, but it would surely be faster than opening a new instance of the table over the network ( I think ).

-- tom

[Al Buchholz]

Re: Any linked children?

Tom, how important is performance in this app?
As far as the OnFetch event is concerned, I was thinking of something very simple like [if (field in child table="" or Null)] then there is no actual link at that point.

That's what I do... you already have the data retrieved for the form to know if there is a child record.

[Tom Cone Jr]

Re: Any linked children?

Thanks guys. Ted & Al's ideas win the kewpie doll.

Here's the code that works just fine without having to open another instance of the linked child table:

'onChange for Cust_id in header for order table

'alert user if linked child records exist.  They probably reflect
'pricing from a different cust_id.

Curr_ord_nbr = parentform:ord_nbr.text

t = table.get("items ordered")

if ut(t.ord_nbr) = ut(curr_ord_nbr) then
    'need to alert user
	ui_msg_box("WARNING","You're changing the cust_id for this order, AFTER having linked one or more items to it." + crlf() +\
	crlf() + "The pricing for the existing items may be wrong." + crlf()+crlf()+\
	"You should check and update the pricing for each item." + crlf()+\
	"The Cust_id in the Cust Pricing column of the grid MUST match your 'NEW' cust_id.",ui_stop_symbol)
end if

[Ted Giles]

Re: Any linked children?

Glad it got sorted Tom.

[G Gabriel]

Re: Any linked children?

Memories...pressed between the pages of my mind..

[barry685]

Re: Any linked children?

I use a different method for testing whether children records exist (because I m not good with functions or xbasic). Please don't laugh. In every child table I have a field named "ONE'. In field rules I default the number 1 to that field (the end user never sees this field). In the parent table I have a field named "Qty_Child".
In the field rules of the child table I use posting to add the 1 to the parent tables "Qty_child" field . So basically the parent record will always keep a count of how many child records there are.

[G Gabriel]

Re: Any linked children?

Barry:
I am not laughing. It's a good idea. Thanks.
But..instead of having the extra field in the child table, what you could do is in the OnSave event of the child, increment the parent. When you delete a child record, decrement it.
Better yet, you could do the same in the field rules using the OnSaveRecord/OnDeleteRecord.
Unfortunately, this will not work for Tom,...it's something you have to do from the very beginning.