MyDAC & C++Builder

[saidus]

Hi !!
I have 2 Tables : SALE & DSALE Master / Detail in myisam format
the probleme is that i can't delete the detail rows when i delete the master row even when i use the onbeforepost event for the master Query
(I used 2 TMyQuery components)
so could you help me resolve this ???
thanks for all

[alec]

onbeforepost event

Maybe OnBeforeDelete event

[saidus]

yes yes yes
i used & use on before delete event!!but don't work

[GEswin]

Perhaps post what you do exactly onBeforeDelete event

[saidus]

On the OnBeforePost and OnBeforeDelete event Detail table i poste some information on Master table

[GEswin]

on master query you should do something similar to this,

Code: Select all

procedure TFrmPacients.DBQpacfitBeforeDelete(DataSet: TDataSet);
begin

 Connection.ExecSQL('delete from detailtable where field = '+BQpacfitcodigo_paciente.AsString,[]);

end;

When you try to delete master field, it deletes details (Of course you have to set correct query).

[alec]

More easy way for delete details:

Code: Select all

MyQueryMaster->SQLDelete = "DELETE master, detail FROM master, detail
WHERE  master.id = detail.master_id and master.id = :Old_id";

or in designtime
MyQuery editor :: Udate SQLs :: Delete

Code: Select all

DELETE master, detail FROM master, detail
WHERE  master.id = detail.master_id and master.id = :Old_id

Note: In this case MyQueryMaster->Options->StrictUpdate must be false

[Ikar]

> i can't delete the detail rows

Please describe it more detailed. Which error message do you get?

[Guest]

Hello !!!
I have a memory access error msg !!
the real problem is :
when deleting master record i use this code in OnBeforeDelete event

Code: Select all

  TableDetail->First(); 
while(!TableDetail->Eof) 
{ 
    TableDetail->Delete(); 
} 

((( note : MasterTable = TMyQuery , DetailTable = TMyTable )))
but in OnAfterDelete and OnAfterPost detail table i have to calculate some value to store in Master table like this

Code: Select all

  
          Extended tot = 0; 
          if(MasterTable->State!=dsEdit) 
             MasterTable->Edit(); 
             DetailTable->First(); 
          while(!DetailTable->Eof) 
          { 
             tot+=DetailTableQT->Value; 
                  DetailTable->Next(); 
          } 
          MasterTableQT->Value    = tot; 
          MasterTable->Post();

thnks for help

[alec]

You can use (for MySQL 4.1+):

Code: Select all

SQL: update master set qt = (select sum(detail.qt) from detail where detail.master_id=master.id ) where id= :MasterId
MasterTable->RefreshRecord();

instead of

Code: Select all

Extended tot = 0; 
          if(MasterTable->State!=dsEdit) 
             MasterTable->Edit(); 
             DetailTable->First(); 
          while(!DetailTable->Eof) 
          { 
             tot+=DetailTableQT->Value; 
                  DetailTable->Next(); 
          } 
          MasterTableQT->Value    = tot; 
          MasterTable->Post();

and http://www.crlab.com/forums/viewtopic.php?t=2139#7116
instead of

Code: Select all

TableDetail->First(); 
while(!TableDetail->Eof) 
{ 
    TableDetail->Delete(); 
} 

It must increase perfomance of your application. Sorry for nag

[Ikar]

> I have a memory access error msg

You should be very careful on writing event handler that changes data. Do not call Cancel, Post, Next, Delete etc in BeforeX or AfterY event handlers.

If you send us (mydac*crlab*com) a complete small sample we will try to answer more detailed.