Solved

creating a table

Posted on 2001-08-18
3
211 Views
Last Modified: 2010-04-04
I create a table like this:

Procedure CreateTable;  
Var Table:TTable;
begin
      Table:=TTable.Create(Form1);
       Table.Active:=False;
       Table.DatabaseName:='MyDB';
       Table.TableName:='Positionen';
       Table.TableType:=ttPARADOX;        
        With Table.FieldDefs DO
         begin
          Clear;
          Add('Position',ftAutoInc,0,True);
          Add('Anzahl',ftFloat,0,False);
          Add('Artikel',ftString,80,False);
          Add('Preis',ftFloat,0,False);
          Add('Rabatt',ftFloat,0,False);
          Add('MWSt',ftString,10,False);
         end;
       With Table.IndexDefs Do
        begin
          Clear;
          Add('','Position',[ixUnique,ixPrimary]);
        end;
       Table.CreateTable;
       Table.Free;
end;

I would like to add an automatic maximum-check for the 'Rabatt'-field (<=50) and a default value of 1 for the 'Anzahl'-field. How can I include this in my 'Procedure CreateTable' ? (Delphi 4)
0
Comment
Question by:jupe
3 Comments
 
LVL 4

Accepted Solution

by:
jsweby earned 100 total points
ID: 6399902
I don't think you can do this using the TTable.CreateTable method; in fact, you are hard pushed to do it even using more complex SQL unless you're using a solid database such as MS SQL Server. Paradox is a very limited database and the CreateTable method doesn't cater for these extra constraints.

However, once created, you can set contraints against individual fields in Delphi. With your TTable component, double-click on it to open the Fields Editor. Right-click in that, and select Add All Fields. Now you can select the fields individually and add constraints to them that are handled by Delphi at run-time, but I'm almost positive that you can't get Paradox to handle them for you.

J.
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6400535
nothing is impossible :-)
(an older sample)

//Set a Valcheck, valcheck may not exist
procedure SetValCheck(Tbl: TTable; Field: TField; MinVal, MaxVal,
           DefVal: Pointer; MinSize,MaxSize,DefSize : Integer; Required: Bool);
var
  hDb: hDbiDb;
  TblDesc: CRTblDesc;
  VChk: pVChkDesc;
  Dir: String;
  NumVChks: Word;
  OpType: CROpType;

begin
  NumVChks := 0;
  SetLength(Dir, dbiMaxNameLen + 1);
  Check(DbiGetDirectory(Tbl.DBHandle, False, PChar(Dir)));
  SetLength(Dir, StrLen(PChar(Dir)));
  VChk := AllocMem(sizeof(VChkDesc));
  try
    FillChar(TblDesc, sizeof(CRTblDesc), #0);

    VChk.iFldNum := Field.Index + 1;
    Tbl.DisableControls;
    Tbl.Close;
    Check(DbiOpenDatabase(nil, nil, dbiReadWrite, dbiOpenExcl,
               nil, 0, nil, nil, hDb));
    Check(DbiSetDirectory(hDb, PChar(Dir)));
    with VChk^ do
    begin
      bRequired := Required;
      if MinVal <> nil then
      begin
        Inc(NumVChks);
        bHasMinVal := True;
        move(MinVal^, aMinVal, MinSize);
      end
      else
        bHasMinVal := False;
      if MaxVal <> nil then

      begin
        Inc(NumVChks);
        bHasMaxVal := True;
        move(MaxVal^, aMaxVal, MaxSize);
      end
      else
        bHasMaxVal := False;
      if DefVal <> nil then
      begin
        Inc(NumVChks);
        bHasDefVal := True;
        move(DefVal^, aDefVal, DefSize);
      end
      else
        bHasDefVal := False;

    end;
    TblDesc.iValChkCount := NumVChks;
    TblDesc.pVChkDesc := VChk;
    OpType := crADD;
    TblDesc.pecrValChkOp := @OpType;

    StrPCopy(TblDesc.szTblName, Tbl.TableName);
    StrCopy(TblDesc.szTblType, szParadox);
    Check(DbiDoRestructure(hDb, 1, @TblDesc, nil, nil, nil, False));
  finally
    Check(DbiCloseDatabase(hDb));
    FreeMem(VChk, sizeof(VChkDesc));
    Tbl.EnableControls;
    Tbl.Open;
  end;
end;

//Help Function to encode bde-date
Function GetBDEDate(Month, Day : Word; Year : SmallInt; var MyDate : DbiDate) : DbiDate;
begin
  Check(DbiDateEncode(Month, Day, Year, MyDate));
  Result := Mydate;
end;


//Table must be opened exclusive,
//a validate check may not exist
procedure TForm1.Button2Click(Sender: TObject);
var
  cmin,cmax,cdef : Double;
  lmin,lmax,ldef : Longint;
  amin,amax,adef : String;
  bdef : Boolean;
  dmin,dmax,ddef : dbiDate;
begin
  //Set validate for numeric Field
  cmin := -2.5;
  cmax := 2.5;
  cdef := 0.01;
  SetValCheck(Table6,Table6.FieldByName('Numeric'),@cmin,@cmax,@cdef,
              SizeOf(cMin),SizeOf(cMax),SizeOf(cdef),True);

  //Set Validate for Integer Field
  lmin := -100;
  lmax := 100;
  ldef := 1;
  SetValCheck(Table6,Table6.FieldByName('Integer'),@lmin,@lmax,@ldef,
              SizeOf(lMin),SizeOf(lMax),SizeOf(ldef),True);

  //Set Validate for Alphanumeric Field
  amin := 'A';
  amax := 'ABCDE';
  adef := 'AB';
  SetValCheck(Table6,Table6.FieldByName('Alpha'),@amin[1],@amax[1],@adef[1],
              length(amin),length(aMax),length(adef),True);

  //Set Validate for Boolean Field (Default only)
  bdef := False;
  SetValCheck(Table6,Table6.FieldByName('Boolean'),Nil,nil,@bdef,
              0,0,SizeOf(bdef),True);

  //Set Validate for DateField
  dMin := GetBDEDate(1,1,1999,dmin);
  dMax := GetBDEDate(12,31,1999,dmax);
  dDef := GetBDEDate(7,1,1999,ddef);
  SetValCheck(Table6,Table6.FieldByName('Date'),@dmin,@dmax,@ddef,
              SizeOf(dMin),SizeOf(dMax),SizeOf(ddef),True);

end;


the bde-unit must be added to the uses clause to get it work

meikl ;-)

0
 

Author Comment

by:jupe
ID: 6400658
Thanks jsweby and meikl. Your help is very much appreciated.

I hoped I could do the trick when defining/creating the table. I thought it should be possible, as you can do it with dbd32.exe.
 
At runtime  it's just changing the maxvalue property of the field.

I give the points to jsweby and will post another 100 points for meikl.

jupe
0

Featured Post

ScreenConnect 6.0 Free Trial

Check out the updates in one game-changing release, ScreenConnect 6.0, based on partner feedback. New features include a redesigned UI that improves session organization and overall user experience. See the enhancements for yourself!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article explains how to create forms/units independent of other forms/units object names in a delphi project. Have you ever created a form for user input in a Delphi project and then had the need to have that same form in a other Delphi proj…
In this tutorial I will show you how to use the Windows Speech API in Delphi. I will only cover basic functions such as text to speech and controlling the speed of the speech. SAPI Installation First you need to install the SAPI type library, th…
This Micro Tutorial will teach you how to censor certain areas of your screen. The example in this video will show a little boy's face being blurred. This will be demonstrated using Adobe Premiere Pro CS6.
This Micro Tutorial hows how you can integrate  Mac OSX to a Windows Active Directory Domain. Apple has made it easy to allow users to bind their macs to a windows domain with relative ease. The following video show how to bind OSX Mavericks to …

777 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