Active link table questions

[MikeC]

Re: Active link table questions

Mauricio, I agree and added your request to an existing Forum Support thread--

http://msgboard.alphasoftware.com/al...334#post450334

[mmaisterrena]

Re: Active link table questions

Thank you Mike I hope that someone at Alpha will take our suggestion

[jmatienza]

Re: Active link table questions

on the second question:
i can't see any advantage in accessing local a5 tables as active-link tables rather than native tables. i have never tried it. in theory it might work using the Visual Fox Pro odbc driver. But if you did, you would loose long field names, all field rules and any extensions that a5 makes to the .dbf format.

Hi, all.

The above statement just caught my attention.

Is it saying that I would not be able to set any field rules for active link tables? Aren't active link tables ordinary dbf tables?

[NoeticCC]

Re: Active link table questions

Is it saying that I would not be able to set any field rules for active link tables?

No, you can set field rules in them but if you used an ODBC driver to link to a DBF table, then you would not be able to use or set the field rules in the table you are linking to...

[jmatienza]

Re: Active link table questions

Thanks, Andrea! I see I interpreted the statement wrong.

So through active-link tables you can make field rules for backend database tables, as long as the backend is not itself a dbf table?

This is a powerful feature indeed.

[NoeticCC]

Re: Active link table questions

Thanks, Andrea! I see I interpreted the statement wrong.

So through active-link tables you can make field rules for backend database tables, as long as the backend is not itself a dbf table?

This is a powerful feature indeed.

You can make rules BUT!!! They only get used if you use the active link table to update - or if you build in a routine that updates the field rules/calcs regularly.

[jmatienza]

Re: Active link table questions

Would you clarify this for me, Andrea?

[Field rules] only get used if you use the active link table to update

Field rules come into play mostly when entering new records, less often when editing existing records. Do these circumstances qualify when using active-link tables, without having to do programming outside the field rules facility?

[NoeticCC]

Re: Active link table questions

Field rules come into play mostly when entering new records, less often when editing existing records. Do these circumstances qualify when using active-link tables, without having to do programming outside the field rules facility?

Yes, definitely no need to generally do any programming for inserting or editing records using active link tables - at least as long as you use a SQL database that has auto-increment capability... with Oracle for example you have to do a bit of coding to make auto-increment ID fields work properly but with mySQL it works wonderfully, and personally I find record amendments, queries etc. in Xbasic EASIER on SQL databases (NOT using active link tables) but that may well be because I have far more experience in SQL than with DBF tables.

In fact I have had great success converting several apps from DBF to mySQL with active links (the active link part so far only used for desktop with my developer copy rather than properly distributed tools as I generally tend to use desktop tools for admin stuff and the rest are WAS apps) where appropriate.

Some of the web-only ones I converted in as little as half an hour, once a recent patch made SQL-db stored images that are NOT Bitmaps possible to be used in web grids etc. by allowing you to specify the image type. E.g. our news & RSS feed pages* are 100% run by Alpha5 now (thanks to the rewrite module in Apache -which works almost exactly the same as stritran_smatch() in Xbasic - I can plant these bits painlessly in our main website which runs on a UNIX box), including a short news listing on the home page and more detailed listings with images.

The news items are currently entered or edited through an active link table, although I have not set any field rules because I am hoping to write a full web admin module for it soon so other users can add news items through a web interface.

http://www.charlesworth.com/

*OK the RSS feed is generated from an Alpha5 WAS page rather than BEING an a5w page of course

[jmatienza]

Re: Active link table questions

Thanks, Andrea, for your incredibly helpful comments. What is it with auto-increment fields? They seem to be such a big issue among SQL databases.

I haven't made the plunge to V9 yet, though I find it terribly attractive. I'm still trying to learn Alpha Five on my current investment (V7). While I don't aspire to reach your level of expertise, I find your experiences very illuminating.

Alpha Five is truly a one-of-a-kind product!

[NoeticCC]

Re: Active link table questions

Thanks, Andrea, for your incredibly helpful comments. What is it with auto-increment fields? They seem to be such a big issue among SQL databases.

I must admit in MS Access I always avoided auto-increments like the plague, however with mySQL, similar to Alpha5, when you optimize the table from mySQL Administrator, it resets the AutoIncrement numbers...

In Oracle on the other hand you need to use sequences to get the same auto-inc effect, which isn't as easy to work with from any application written against Oracle. It's not a big deal though, you just have to add a line of code in the CanInsertRecord event on a web grid (or OnSave events in browses for desktop etc) to grab the next sequence if a new item is inserted, e.g.

Dim NextVal as c
NextVal = sql_records_get("::name::TRK", "DUAL", "1=1","ELOGGER_USER_INFO_SEQ.NEXTVAL")

DataSubmitted.EUI_ID = NextVal

And yes, Alpha5 is really rather special - I was impressed with the basic functions, but when I realised just how much you can do with a bit of coding I was blown away! :)

[kthibeault1965]

Re: Active link table questions

I have a client who is working to migrate his fully working dbf based application to client server. As the first engine to try, they chose mysql. Unfortunately the primary function of the desktop application to manage set data (by saving parent id�s in each new child record) does not work. (or I have not configured it properly)

We do a simple one to many, two table set, using active link tables. Then to test, open the default form, add a parent record, then add a child record. The form sometimes give the illusion that it works, depending on the alpha build, but it does not.

Where the parent id should go in the child record, we get a null value, making the set totally unusable obviously. The child record gets created, but the link is never established because the null value never links to the parent.

[Selwyn Rabins]

Re: Active link table questions

I have a client who is working to migrate his fully working dbf based application to client server. As the first engine to try, they chose mysql. Unfortunately the primary function of the desktop application to manage set data (by saving parent id�s in each new child record) does not work. (or I have not configured it properly)

We do a simple one to many, two table set, using active link tables. Then to test, open the default form, add a parent record, then add a child record. The form sometimes give the illusion that it works, depending on the alpha build, but it does not.

Where the parent id should go in the child record, we get a null value, making the set totally unusable obviously. The child record gets created, but the link is never established because the null value never links to the parent.

I an unable to repeat any problem using my test data.

http://screencast.com/t/fH5NslFA

[Selwyn Rabins]

Re: Active link table questions

I was able to repeat the problem using your test data.


you need to change the definition of your child_row table.

you currently have the header_id column set to allow null values.

this does not make sense as this is the linking field in the set.

if you edit the structure of the table and change the header_id column to be 'not null' then it will work.

we will change a5 so that in future, even if the column is set to nullable, it will work.

but in the mean time, the work around is trivial.