如何将表中的值保存到另一个表delphi中

Question

I am using delphi rad studio and i am a beginner in this. I am trying to insert values into a table from another table which contains just IDs. I have some comboboxes filled with ID's from a table and then i want to insert these values into another table. To be more specific i have a table that contains the specifications about cars and i want to save those into a table which contains information of rental this cars. I have tried much but i didn't get the answer. Here is the code for combobox :

    procedure TForm13.DBLookupComboBox1Click(Sender: TObject);
    begin
    adomarca.SQL.Text :=    ' SELECT tabel_Marca.Marca from Tabel_Masini ' +
     'join tabel_Marca on tabel_masini.id_Marca=tabel_marca.id_Marca ' ;

     SELF.ADOmarca.ExecSQL;
     SELF.ADOmarca.Open;
     ADOmarca.Prepared := TRUE;
     end;        

And this is the code for the save button:

     procedure TForm13.button2click(Sender: TObject);

      begin
      Comanda := 'Insert into Tabel_Inchirieri (id_Client, id_Marca, 
                id_Model, id_Transmisie, id_Caroserie, id_Culoare, 
                   id_Combustibil, Ziua_Inchirierii, Ziua_Restituirii, 
            Nr_zile_inchiriate) ' +
        // 'select * from tabel_masini ' +
         'Values (' + inttostr(DBLOOKUPCOMBOBOX8.keyvalue) + ',' 
         +inttostr(DBLOOKUPCOMBOBOX1.keyvalue) + ',' + 
          inttostr(DBLOOKUPCOMBOBOX2.keyvalue) + ',' + 
          inttostr(DBLOOKUPCOMBOBOX3.keyvalue) + ',' + 
          inttostr(DBLOOKUPCOMBOBOX4.keyvalue)+ ',' + 
           inttostr(DBLOOKUPCOMBOBOX5.keyvalue) + ',' + 
          inttostr(DBLOOKUPCOMBOBOX6.keyvalue)+ ',' + 
           quotedstr(formatdatetime('yyyy-mm-dd',DateTimePicker1.Date))+ 
          ','+ quotedstr(formatdatetime('yyyy-mm- 
           dd',DateTimePicker2.Date))+',' + 
          inttostr(daysbetween(DateTimePicker2.Date, 
        DateTimePicker1.Date))+')';
         Qcomanda.SQL.Add(Comanda);

         try
           Qcomanda.ExecSQL ;
         finally
            ShowMessage('Comanda a fost salvata cu succes ! ');

          end;


           end;

Thank you very much.

Answer 1

You don't say what RDMS you are using, but there are ways to do this entirely in SQL that should work with at least MS Sql Server and MS Access, which are probably the mostly commonly used RDMSs with ADO.

If you are intending your copying operation to populate a new table on the server you can use SQL like this

   SELECT
     [FieldList]
   INTO
     MyNewTable
   FROM
     [tables and join condition]

You can easily google an example of this, see fi http://www.vb-helper.com/howto_ado_select_into.html

If you want to copy rows into an existing table you can use the

   INSERT INTO
     [tablename]
   SELECT
     [fieldlist]
   FROM
     [tables and join condition]

see fi https://docs.microsoft.com/en-us/office/client-developer/access/desktop-database-reference/insert-into-statement-microsoft-access-sql

You can execute these SQL statements either in a Delphi app or, if using MS SQL Server, using the SQL Server Management Studio.

Either method, unlike your proposed code, would copy the selected records all in one go, without any need for a record-by-record, column-by-column copying operation, and you should find either method extremely fast compared to client-side record-by-record copying. However, you need to be careful if a very large number of records is involved: doing them all in one go means that they are potentially wrapped up in a huge server-side transaction which could exhaust the server's resources, so in that situation it would probably be better to split the copying up into a series of smaller batches, if that's practicable.