Solved

Add a column to db-tables

Posted on 1998-05-25
15
265 Views
Last Modified: 2010-04-06
I a couple of tables and have to add another Column to the existing table, and then save the table with the new Column, how do I do that, btw I'm using Delphi 2.0.
0
Comment
Question by:koger
  • 7
  • 4
  • 2
  • +2
15 Comments
 
LVL 1

Expert Comment

by:jturpin
Comment Utility
The best way to do that is by using the
"Borland Database Desktop" under "Tools"
(I think) on the main Delphi2 menu.

John.
0
 

Author Comment

by:koger
Comment Utility
Ehh, well, I need to create a program that can add a column, so what I need is some code ;-)
0
 
LVL 1

Expert Comment

by:jturpin
Comment Utility
Ok you seem to have missed that point in
your original question.

I don't believe you can simply add a column
to a table. I usually clone the structure
of the original table, add the column, and then
select the info I need. But you could try
simply adding the column to the existing table
if you want, although I think you will get
an error.

The code for adding a column to the table is:

   OriginalTable.FieldDefs.Add(FieldName,
      FieldType,FieldLen,false);

   e.g.
      Table1.FieldDefs.Add('SupCarry',ftString,SupLEN,false);
      Table1.FieldDefs.Add('PayCarAll',ftBoolean,0,false);
      Table1.FieldDefs.Add('Rate',ftFloat,0,false);
      Table1.Exclusive:= true;
   
      Table1.CreateTable;

I hope that helps,

John.
0
 

Author Comment

by:koger
Comment Utility
To jturpin

Here is a ex. of the code I use:

Table1.FieldDefs.Add('NewEntry:', ftString, 25, False);
Table1.CreateTable;

This will causs all the existing information in the table to be erased :-(, how is it possible to keep the existing information and still add an extra column?
0
 
LVL 5

Expert Comment

by:ronit051397
Comment Utility
Use SQL. For adding a new field, called 'TEST' to the ANIMALS table write:

with Query1 do
begin
  DatabaseName:='DBDEMOS';
  SQL.Text:='ALTER TABLE "ANIMALS.dbf" ADD TEST SMALLINT';
  ExecSQL;
end;

0
 

Author Comment

by:koger
Comment Utility
It must be possible to add a column, without using SQL.
0
 
LVL 7

Expert Comment

by:BlackMan
Comment Utility
You need to use the dbiDoRestructor procedure. There is an example at http://www.inprise.com/devsupport/bde/bdeapiex/dbidorestructure.html
0
Highfive + Dolby Voice = No More Audio Complaints!

Poor audio quality is one of the top reasons people don’t use video conferencing. Get the crispest, clearest audio powered by Dolby Voice in every meeting. Highfive and Dolby Voice deliver the best video conferencing and audio experience for every meeting and every room.

 

Author Comment

by:koger
Comment Utility
Ok I have tried it all, and I simply don't get it, so I will take it one more time

I have to add a column to a paradox table, I need some code for Delphi 2.0 that does the trick.

The existing columns was made with fielddefs

with Table1.FieldDefs do
begin
  Clear;
  Add('Column1', ftString, 50, False);
  Add('Column2', ftString, 50, False);
end;
Table1.CreateTable;

if I try to add another column after table1.createtable was used,
I get an error.

Table1.FieldDefs.Add('Field3', ftString, 25, False);
Table1.FieldDefs.Update;
DBEdit3.DataField := 'Field3';  <-- error 'Field3 dosn't exist!'

If I call Table1.CreateTable again the whole table will be erased, all the information written in the table are lost.

Would someone give me an example that matches my table?
0
 
LVL 5

Expert Comment

by:ronit051397
Comment Utility
What's wrong with SQL?
0
 
LVL 1

Expert Comment

by:Marcius
Comment Utility
The use of fielddefs will not create a row in the underlying table. It is an operator designed to manipulate TDataset, not the underlying table.

I really think that the best solution is to use SQL. Other than that, you can re-create a new table each time you want to add a column, migrate the data, then destroy the old table. As you can see, SQL is the cleaner option.
0
 

Author Comment

by:koger
Comment Utility
Ok, how do I use SQL?
0
 
LVL 5

Expert Comment

by:ronit051397
Comment Utility
I have already posted the answer on SQL and you rejected it.
0
 

Author Comment

by:koger
Comment Utility
To Ronit.

The reason that I really didn't want(ed) to use SQL, is that my application don't use SQL and I haven't used SQL before.

you gave me this SQL statement,

  SQL.Text:='ALTER TABLE "ANIMALS.dbf" ADD TEST SMALLINT';

I need a string field with the length 25, I haven't got any manual that covers SQL statements, so it is a bit tricky to figure out how the statement should look, will help me with that?
0
 
LVL 5

Accepted Solution

by:
ronit051397 earned 100 total points
Comment Utility
This must be done exclusively, meaning the table cannot be active in your application or another application, while SQL is executing:

with Query1 do
begin
    DatabaseName:='DBDEMOS';
    SQL.Text:='ALTER TABLE "ANIMALS.dbf" ADD TEST CHAR(25)';
    ExecSQL;
 end;

for more information on SQL statements see:
C:\Program Files\Borland\Common Files\BDE\Localsql.hlp
0
 

Author Comment

by:koger
Comment Utility
Thanx!!
0

Featured Post

Top 6 Sources for Identifying Threat Actor TTPs

Understanding your enemy is essential. These six sources will help you identify the most popular threat actor tactics, techniques, and procedures (TTPs).

Join & Write a Comment

A lot of questions regard threads in Delphi.   One of the more specific questions is how to show progress of the thread.   Updating a progressbar from inside a thread is a mistake. A solution to this would be to send a synchronized message to the…
Introduction I have seen many questions in this Delphi topic area where queries in threads are needed or suggested. I know bumped into a similar need. This article will address some of the concepts when dealing with a multithreaded delphi database…
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
This tutorial demonstrates a quick way of adding group price to multiple Magento products.

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

10 Experts available now in Live!

Get 1:1 Help Now