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Code: Select all

  SQL_Query.Execute; //Opens data set as Select * from TM
  <here I chose a record to modify> 
  UQ_To_X_rec(SQL_Query, X_rec); <and store it into record variable>
  try
      try
        SQL_Query.Lock;
        SQL_Query_D.Execute;  //Opens data set as Select * from TD 
                              //                  where TD.Link=TM.Link
        <detail data are stored in dynamic array>  
        <here on the form I change the Master and/or Detail data 
            stored in the record variable and the array for details>  

        if OK_1 then begin // if user click OK button on the form to accept changes
          SQL_Query.Edit;
          X_rec_To_UQ(SQL_Query, X_rec);  <make changes in locked record in TM>
          
          <here there are updates for details in TD table (SQL_Query_D) = OK_2>
          if OK_2                  // if update of details went OK
          then SQL_Query.Post      // for commit changes
          else SQL_Query.Cancel;   // for rollback changes
        end;

      finally
        SQL_Query.UnLock;
      end;
    except
      SQL_Query.Cancel;
      MsgBox('Error .....',mfOK);
    end;

Code: Select all

   if <lock record in Master table to prevent it for edition by other users>
   then begin
     <read the record to record variable>  
     <Read detail data into an array>
     <Modify data in memory> 
     if <user accepts changes> 
     then begin
        <Begin Transaction>
        if <update master record> and <update detail data>
        then <End Transaction = Commit all changes>
        else <Abort Transaction = cancel all changes>  
     end;
   end 
   else begin
     MsgBox('Record is Locked by other user');
   end; 

Code: Select all

  MasterQuery.LockMode := lmOptimistic;
  MasterQuery.Lock; // start a transaction and lock the current master record

  // do some changes in master and detail

  if ... then
    UniConnection.Commit  //apply all changes and unlock the master record
  else
    UniConnection.Rollback; // roll back all changes and unlock the master record

Code: Select all

    SQL_Query.Connection.StartTransaction;
    try
      SQL_Query.Lock;
      try
        < changes > 
      finally
        SQL_Query.UnLock;
        SQL_Query.Connection.Commit;
      end;
    except
      SQL_Query.Connection.Rollback;
      MsgBox('Error ....');
    end;

Code: Select all

SQL_Query.Connection.StartTransaction; // Start transaction
    try
      SQL_Query.Lock; // Lock record and create savepoint LOCK_SQL_Query
      try
        < changes > 
      finally
        SQL_Query.UnLock; // Roll back to save point LOCK_SQL_Query
        SQL_Query.Connection.Commit; // Commit transaction. But since it was rolled back to the save point LOCK_SQL_Query on the previous line, nothing will be changed in the data base. 
      end;
    except
      SQL_Query.Connection.Rollback;
      MsgBox('Error ....');
    end;

Code: Select all

  SQL_Query.Connection.StartTransaction; // Start transaction
  try
    SQL_Query.Lock; // Lock record and create savepoint LOCK_SQL_Query 

Code: Select all

  UniQuery1.Options.StrictUpdate := False;
  UniQuery1.SQLLock := 'LOCK TABLE YourTable IN ACCESS EXCLUSIVE MODE;';
  UniQuery1.Lock;

Code: Select all

  Result:=false; 
  SQL_Query.Connection.StartTransaction;
  try
    SQL_Query.Lock;
    UQ_to_KS_rec(SQL_Query, X_rec);
    Detail_Read(X_rec.Id); //reads details from several tables by master's Id

    F_ES_E_KS:=TF_ES_E_KS.Create(self);
    OK_1:= F_ES_E_KS.Edit(X_rec); //here user makes changes and accepts them
    F_ES_E_KS.RELEASE;

    if OK_1 then begin
      try
        SQL_Query.Edit;
        KS_rec_to_UQ(SQL_Query, X_rec);  
        SQL_Query.Post;  //it is necessary to check constrains i.e. unique indexes
        if  Detail_Write(X_rec) then begin //store details
          SQL_Query.Connection.Commit;
          SQL_Query.Refresh; 
          Result:=true;
        end else begin
          SQL_Query.Cancel;
          SQL_Query.Connection.Rollback;
        end;
      except
        SQL_Query.Cancel;
        SQL_Query.Connection.Rollback;
        MsgBox('Error during update !!!',mfOK);
      end;
    end else begin
      SQL_Query.Cancel;
      SQL_Query.Connection.Rollback;
    end;
  except
    SQL_Query.Connection.Rollback;
    MsgBox('Record is locked by another user');
  end;

Code: Select all

      except
        SQL_Query.Cancel;
        SQL_Query.Connection.Rollback;
        MsgBox('Error during update !!!',mfOK);
      end;