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Adding new fields to a Paradox table from Delphi

Posted on 1999-07-05
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Last Modified: 2010-04-06
I want my program to add a field to the database table if
the field does not exist!
I am using Paradox 7, and Delphi4

Please give me an example!
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Question by:KjellR
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2 Comments
 
LVL 27

Accepted Solution

by:
kretzschmar earned 200 total points
ID: 1386197
hi KjellR,

directly from borland

http://www.borland.com/devsupport/bde/bdeapiex/dbidorestructure.html


Example 10: Add a field to a Paradox or dBASE table.

   This example will add a field to the end of an existing table.
   NOTE: You must fill in all options in the ChangeRec with 0 or '' if the option is not used in the restructure.
   FillChar can be used to do this: Fillchar(MyChangeRec, sizeof(MyChangeRec), 0);
   This example uses the following input:
   AddField(Table1, MyChangeRec);
   ChangeRec is defind as follows:

   ChangeRec = packed record
       szName: DBINAME;
       iType: word;
       iSubType: word;
       iLength: word;
       iPrecision: byte;
     end;

   The function is defined as follows:

   procedure AddField(Table: TTable; NewField: ChangeRec);
   var
     Props: CURProps;
     hDb: hDBIDb;
     TableDesc: CRTblDesc;
     pFlds: pFLDDesc;
     pOp: pCROpType;
     B: byte;

   begin
     // Make sure the table is open exclusively so we can get the db handle...
     if Table.Active = False then
       raise EDatabaseError.Create('Table must be opened to restructure');
     if Table.Exclusive = False then
       raise EDatabaseError.Create('Table must be opened exclusively to restructure');

     // Get the table properties to determine table type...
     Check(DbiSetProp(hDBIObj(Table.Handle), curxltMODE, integer(xltNONE)));
     Check(DbiGetCursorProps(Table.Handle, Props));
     pFlds := AllocMem((Table.FieldCount + 1) * sizeof(FLDDesc));
     FillChar(pFlds^, (Table.FieldCount + 1) * sizeof(FLDDesc), 0);
     Check(DbiGetFieldDescs(Table.handle, pFlds));

     for B := 1 to Table.FieldCount do begin
       pFlds^.iFldNum := B;
       Inc(pFlds, 1);
     end;
     try
       StrCopy(pFlds^.szName, NewField.szName);
       pFlds^.iFldType := NewField.iType;
       pFlds^.iSubType := NewField.iSubType;
       pFlds^.iUnits1  := NewField.iLength;
       pFlds^.iUnits2  := NewField.iPrecision;
       pFlds^.iFldNum  := Table.FieldCount + 1;
     finally
       Dec(pFlds, Table.FieldCount);
     end;

     pOp := AllocMem((Table.FieldCount + 1) * sizeof(CROpType));
     Inc(pOp, Table.FieldCount);
     pOp^ := crADD;
     Dec(pOp, Table.FieldCount);

     // Blank out the structure...
     FillChar(TableDesc, sizeof(TableDesc), 0);
     //  Get the database handle from the table's cursor handle...
     Check(DbiGetObjFromObj(hDBIObj(Table.Handle), objDATABASE, hDBIObj(hDb)));
     // Put the table name in the table descriptor...
     StrPCopy(TableDesc.szTblName, Table.TableName);
     // Put the table type in the table descriptor...
     StrPCopy(TableDesc.szTblType, Props.szTableType);
     // Close the table so the restructure can complete...
     TableDesc.iFldCount := Table.FieldCount + 1;
     Tabledesc.pfldDesc := pFlds;
     TableDesc.pecrFldOp := pOp;
     Table.Close;
     // Call DbiDoRestructure...
     try
       Check(DbiDoRestructure(hDb, 1, @TableDesc, nil, nil, nil, FALSE));
     finally
       FreeMem(pFlds);
       FreeMem(pOp);
       Table.Open;
     end;
   end;

meikl
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Author Comment

by:KjellR
ID: 1386198
Thank you for your quick response, the points are yours :)
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