Russell,
you made it much clearer than I did :-)
I actually use TFieldType from Delphi and only support 4 types. I dont
have any issue with searching
where (Field_Type = ftInteger) and (Field_Data between 5 and 6)
where (Field_Type = ftstring) and (Field_Data = 'GLUCOSE')
work just fine.
Rohit
On 6/03/2013 12:45 p.m., russell wrote:
Rohit's method is like one I use that allows users to "add fields".
Users add records to an existing table. The program manages these
records (so it appears to users) as if they are fields.
The field types are important if you allow users to store data that
will not fit into a fixed length field.
I allow three data types: Text, FileNames and Memo. The first two are
single lines of text of any length and the third handles multi-line data.
All three types are stored as BLOBs in a Firebird db file.
A "con" is these fields are not easily searched ... but I do not need
this ability.
Best regards,
Russell
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Rohit Gupta
*Sent:* Wednesday, 6 March 2013 11:49 a.m.
*To:* NZ Borland Developers Group - Delphi List
*Cc:* List NZ Borland Developers Group - Delphi
*Subject:* Re: [DUG] Runtime user defined fields
I would consider having a generic table where you soft-add the fields
Ref_Num : autoinc
Owner_Num : int64
Field_Name : string (16)
Field_Type : integer // ord(TFieldType)
Field_Data : string (255) // store everything as string but the type
above tells you what it is
This way you dont alter the database. You dont have to worry about
indexes etc. Everyones database is the same. Yet you can search for
data for a particular field name. I am actually using this structure
in a three projects.
Regards
Rohit
On 6/03/2013 10:41 a.m., Steve Peacocke wrote:
Hi everyone,
I've been away from programming for a while so please excuse the
seemingly simple question.
I'm designing a user interface for a new application and wondered if
there was a generally accepted way that this "should" be done.
The application will allow end users to edit their forms allowing them
to add, move, and remove fields at runtime. I'm using MySQL but I was
wondering if there was an accepted way of adding and changing fields
to a database.
I know I can use SQL for this but I also don't want to make every
application unable to be managed or upgraded. Perhaps I can ensure
that the 3-4 permanent fields are never able to be altered (ID, Name,
etc) but allow the user (through a suitable user-friendly interface)
to go crazy adding such fields as My_favourite_colour, Rating,
Priority, Notes, etc. etc.
I'm able to give a suitable user-friendly interface to allow them to
physically alter the Delphi form at runtime, but wondered about the
"most appropriate way" to modify the fields to the database.
1. I could simply add fields using SQL's ALTER TABLE
2. I could add another table with fields such as TableName, FieldName,
Type, etc.. and add to that
3. Some other spiffy way that you people will suggest that I haven't
even thought of yet.
Any suggestions?
Steve Peacocke
+64 220 612-611
http://www.nzorient.co.nz
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Technical Director
Computer Fanatics Ltd
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*Fax *4892290
*Web *www.cfl.co.nz
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