Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

creating a table

Posted on 2001-08-18
3
Medium Priority
?
230 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
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
3 Comments
 
LVL 4

Accepted Solution

by:
jsweby earned 400 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

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

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

Have you ever had your Delphi form/application just hanging while waiting for data to load? This is the article to read if you want to learn some things about adding threads for data loading in the background. First, I'll setup a general applica…
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…
Visualize your data even better in Access queries. Given a date and a value, this lesson shows how to compare that value with the previous value, calculate the difference, and display a circle if the value is the same, an up triangle if it increased…
In this video, Percona Solution Engineer Rick Golba discuss how (and why) you implement high availability in a database environment. To discuss how Percona Consulting can help with your design and architecture needs for your database and infrastr…
Suggested Courses

715 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