I'm using Lazarus and a Firebird database to display several Forms. The datasource related query_1 joins two, sometimes three tables, and the data is shown in TDBEdit displays.
I need to place two buttons on forms: MODIFY and SAVE for the users. If data was only one table MODIFY would basically call Query_1. Edit, and SAVE would ApplyUpdates. With the joined tables in the query ApplyUpdates would give an error, but thought I could have the SAVE call a query_2 to select the record in one table (and later the corresponding one in the othery -all in the same transaction) and Edit the modified field taking the value from the TDBEdit.Text or the modified dataset’s fields, but this does not work because Lazarus/Firebirs does not let the user write into the TDBEdit of the joined table even though they are not ReadOnly.
I could instead use simple TEdits , populating them from Qry_1 fields to display the data and make changes, and then use the modified texts to edit the corresponding fields, but this will require a lot of changes as well as programing to keep the user from introducing garbage, and seems not to be the best solution.
I believe I am complicating something that should be more "standard" and simple but have not found other solutions. Would appreciate somebody pointing me to the right “normal” practice.
Related
This feels like it should be a common requirement, but I'm not sure how best to implement the requirement.
I'm going to make up a really simple example. It's similar enough to what I actually need, without getting over-complicated.
Imagine we have a table called transport and it has the following columns:
type
model_name
size
number_of_wheels
fuel
maximum_passenger_count
We want to store all sorts of different types of transportation in this table, but not every type will have values in every column. Imagine the commonality is a lot higher, as this is a bit of fake example.
Here's a few examples of how this might work in practice:
type = cycle, we ban fuel, as it's not relevant for a cycle
type = bus, all columns are valid
type = sledge, we ban number_of_wheels, as sledges don't have wheels, we also ban fuel
type = car, all columns are valid
I want my UI to show a grid with a list of all the rows in the transport table. Users can edit the data directly in the grid and add new rows. When they add a new row, they're forced to pick the transport type in a dropdown before it appears in the grid. They then complete the details. All the values are optional, apart from the ones we explicitly don't want to record a value for, where we expect to not see anything at all.
I can see a number of ways to implement this, but none of them seems like a complete solution:
I could put this logic into the UI, enabling/ disabling grid cells based on type. But there's nothing to stop someone directly inserting data into the "wrong" columns in the backend of the database or via the API, which would then come through into the UI unless I added a rule to also mask out values in disabled cells. Making changes to which columns are restricted per transport type would be very difficult
I could put this logic into the API, raising an error if someone enters data into a cell that should be disallowed. This closes one gap for insertion to the database via the API, but SQL scripts would still allow entry into the "wrong" column. Also, the user experience would suck, as users would have to guess which columns to complete and which to leave blank. It would still be difficult to make changes to which columns are allowed/ restricted
I could add a trigger to the database, maybe to set the values to NULL if they shouldn't be allowed, but this seems clunky and users would not understand what was happening
I could add a generated column, but this doesn't help if I sometimes need to set a value and sometimes don't
I could just allow the unnecessary data to be stored in the database, then hide it by using a view to report it back. It doesn't seem great, as users would still see data disappearing from the UI with no explanation
I could add a second table, storing a matrix of which values are allowed and which are restricted by type. The API, UI and database could all implement this list using different mechanisms - this comes with the advantage of having a single place to make changes that will immediately be reflected across the entire system, but it's a lot of work and I have lots of these tables that work the same way
I have a situation as described in the ExtbaseFluid book:
I would like to store information in the intermediate table which is not recommended at all.
Here is a cite from the warning box of the above linked book chapter:
Do not store data in the Intermediate Table that concern the Domain. Though TYPO3 supports this (especially in combination with Inline Relational Record Editing (IRRE) but this is always a sign that further improvements can be made to your Domain Model. Intermediate Tables are and should always be tools for storing relationships and nothing else.
Let’s say you want to store a CD with its containing music tracks: CD -- m:n (Intermediate Table) -- Song. The track number may be stored in a field of the Intermediate Table. However, the track should be stored as a separate domain object, and the connection be realized as CD -- 1:n -- Track -- n:1 -- Song.
So I want not to do what is not recommended. But thinking about the workflow for the editor that results of the recommended solution rises a few question for me.
To stay with this example I would need the following tables:
tx_extname_domain_model_cd
tx_extname_domain_model_cd_track_mm
tx_extname_domain_model_track (which holds the track number)
tx_extname_domain_model_track_song_mm
tx_extname_domain_model_song
From what I know this would end in the situation that the editor would need to create following records:
one record for the cd
one record for the song
now the editor can create one record for the track.
There the track number is added.
Furthermore the cd record needs to be assigned as well as the song.
So here are my questions:
I guess this workflow cannot be improved with some (to me unknown) TCA setup?
An editor cannot directly reach the song when the cd record is opened?
Instead first she / he has to open the track record and can from there navigate to the song?
Is it really that bad to store data in the intermediate table? The TYPO3 table sys_file_reference does the same!? But I wonder how those data could be shown (because IRRE is not possible because it shall only be used for 1:n relations (source).
The question you have to ask yourself is: Do I want to do coding by the book, or do I want to create a pragmatic approach to solve a customer's problem?
In this specific case the additional problem is, that the people who originally invented Extbase had a quite sophisticated and academic approach, but when it comes to a pragmatic use and performance, they were blocked by their own rules and stuck with coding by the book.
Especially this example and the warning message shows a way of thinking that was one of the reasons, why I never actually used Extbase but went for Core-API methods to create performant and pragmatic queries to get the desired result sets. Now that we've got Doctrine under the hood, this works like a charm even with quite exotic DB flavors.
Of course intermediate tables are a good idea and of course those intermediate tables can and should be enriched with additional data fields, that do not require a 3rd, 4th or nth table to store i.e. a simple set of dropdown options, since this can easily be handled with attributes configured in TCA, as it is shown here: https://docs.typo3.org/m/typo3/reference-tca/master/en-us/ColumnsConfig/Type/Inline/Examples.html
sys_file_reference is the most prominent example since it provides exactly that kind of additional information that should not be pumped into additional tables - and guess what, the TYPO3 core does not make use of a single line of Extbase code to deal with that data or almost any other data of the core tables.
To answer your last question: Take a look at the good old IRRE Tutorial to get a clue how to do m:n connections with intermediate inline tables.
https://docs.typo3.org/typo3cms/extensions/irre_tutorial/0.4.0/Manual/Index.html#intermediate-tables-for-m-n-relations
Depends on the issue, sometimes the intermediate table is an entity, sometimes not. In this example the intermediate table is the track, which would contain: [uid, cd, song, track_no, ... (whatever else needed to define the track)]
Be carefull when you define your data, that you do not make it too advanced.
I am working on Access 2007. I have a table with some fields in it. I had created a form from the table and one of the fields of the table is a concatenation of 2 fields from the same table.
There are 2 fields OppNo and Material in the table. I had created a form with these (and others in the table) fields. There is another field OppMat which is blank in the table. However, I had got the data into OppMat field populated as a concatenation of OppNo and Material fields in the form. I am now looking at having the table updated with the data of OppMat from the form to the same corresponding field in the table.
Kindly advise as how I could achieve this.
Thanks and regards,
This might be possible if these cases are met:
The field OppMat ALWAYS has the same structure and you can assure that it does.
Users will not be able or very unlikely to deviate from this structure.
Notably you should use something like Left(), Right(), Mid() and so on. Whatever works best for your structure. You can use the string modifiers: https://msdn.microsoft.com/en-us/library/dd789093.aspx
On the other hand I must admit that I am sceptical if your solutions is the best. Here are my reasons:
Users are unpredictable and will continously deviate from your intended way to use the application.
Using the string functions and fixating on one structure makes your code construction inflexible, hard to maintain if changes occur and prone to errors.
The alternatives seem to be better with little drawback.
My suggestions for alternatives:
Use one textbox for each field so that you have two textboxes. You can even position them that way that it almost looks like it is continous text. But not too much otherwise the user will beconfused.
You can add a label that shows your concatenated fields. But for input you use two different textboxes.
Cheers!
I have a situation where we have a base recordset with about one hundred thousand records. And, we are creating a separate application that shares some of the dataset, but not most, so we are creating a detail table that has a one to one relationship with the original table. What I want to do is pull the existing information from the original table and display it as read only, but I want the fields in the detail table to be writeable.
I've started by creating a listing with the contents of the original table, I want the user to be able to seemlessly hit "edit" by an entry and be taken to the form to create the detail record, click save, and have it update, or create the record.
So, what is the best way to do this?
This question is old, but in order to help future searchers...
Including a related table in a form is handled automatically if your DBIx::Class result sources are correctly setup. A related table can be pulled into the form by simply defining a compound field using the relationship name of the other field and defining subfields with the names of the columns in the related table.
See: HTML::FormHandler::Manual::Fields
And: HTML::FormHandler::Manual::Database
This isn't a real answer, in that I can't really provide you with a solution, but I can hopefully provide you with somewhere to start. I think you need to define a form in HTML::FormHandler which represents a single row from your detail table, then build your read-only form from multiple instances of single-row form. This article describes the problem and a partial solution much better than I have:
http://catdev.blogspot.com/2009/05/defining-form-processing-problem.html
I'm fairly new to Perl and HTML::FormHandler, and there's a good chance that there is a better way of doing this. It's a problem that I have solved 'manually' in PHP before, but one which I am sure I will come across in Perl.
What are some possible designs to deal with frequently changing data forms?
I have a basic CRUD web application where the main data entry form changes yearly. So each record should be tied to a specific version of the form. This requirement is kind of new, so the existing application was not built with this in mind.
I'm looking for different ways of handling this, hoping to avoid future technical debt. Here are some options I've come up with:
Create a new object, UI and set of tables for each version. This is obviously the most naive approach.
Keep adding all the fields to the same object and DB tables, but show/hide them based on the form version. This will become a mess after a few changes.
Build form definitions, then dynamically build the UI and store the data as some dictionary like format (e.g. JSON/XML or maybe an document oriented database) I think this is going to be too complex for the scope of this app, especially for the UI.
What other possibilities are there? Does anyone have experience doing this? I'm looking for some design patterns to help deal with the complexity.
First, I will speak to your solutions above and then I will give my answer.
Creating a new table for each
version is going to require new
programming every year since you will
not be able to dynamically join to
the new table and include the new
columns easily. That seems pretty obvious and really makes this a bad choice.
The issues you mentioned with adding
the columns to the same form are
correct. Also, whatever database you
are using has a max on how many
columns it can handle and how many
bytes it can have in a row. That could become another concern.
The third option I think is the
closest to what you want. I would
not store the new column data in a
JSON/XML unless it is for duplication
to increase speed. I think this is
your best option
The only option you didn't mention
was storing all of the data in 1
database field and using XML to
parse. This option would make it
tough to query and write reports
against.
If I had to do this:
The first table would have the
columns ID (seeded), Name,
InputType, CreateDate,
ExpirationDate, and CssClass. I
would call it tbInputs.
The second table would have the have
5 columns, ID, Input_ID (with FK to
tbInputs.ID), Entry_ID (with FK to
the main/original table) value, and
CreateDate. The FK to the
main/original table would allow you
to find what items were attached to
what form entry. I would call this
table tbInputValues.
If you don't
plan on having that base table then
I would use a simply table that tracks the creation date, creator ID,
and the form_id.
Once you have those you will just need to create a dynamic form that pulls back all of the inputs that are currently active and display them. I would put all of the dynamic controls inside of some kind of container like a <div> since it will allow you to loop through them without knowing the name of every element. Then insert into tbInputValues the ID of the input and its value.
Create a form to add or remove an
input. This would mean you would
not have much if any maintenance
work to do each year.
I think this solution may not seem like the most eloquent but if executed correctly I do think it is your most flexible solution that requires the least amount of technical debt.
I think the third approach (XML) is the most flexible. A simple XML structure is generated very fast and can be easily versioned and validated against an XSD.
You'd have a table holding the XML in one column and the year/version this xml applies to.
Generating UI code based on the schema is basically a bad idea. If you do not require extensive validation, you can opt for a simple editable table.
If you need a custom form every year, I'd look at it as kind of a job guarantee :-) It's important to make the versioning mechanism and extension transparent and explicit though.
For this particular app, we decided to deal with the problem as if there was one form that continuously grows. Due to the nature of the form this seemed more natural than more explicit separation. We will have a mapping of year->field for parts of the application that do need to know which data is for which year.
For the UI, we will be creating a new page for each year's form. Dynamic form creation is far too complex in this situation.