Commands out of sync; you can't run this command now

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Category: dbExpress
Published on Thursday, 25 November 2010 07:57
Hits: 355

If you are receiving error: "Commands out of sync; you can't run this command now" in dbExpress / MySQL connection, then check your query, probably it's something wrong...

 

Also, with connection to MySQL you can't do "select" SQL statement inside transaction, for example:

var
  DBXTran: TDBXTransaction;
begin
  sql1.Close;
  sql1.SQL.Clear;
  sql1.SQL.Text := 'select * from table_one';
  sql1.Open;

  cds2.Open;
  try
    DBXTran := connnection1.BeginTransaction;


    cds2.Append;

    cds2.FieldByName('MyField').AsString := 'test';

    cds2.Post;
    cds2.ApplyUpdates(0);
    connnection1.CommitFreeAndNil(DBXTran);
  finally
    connnection1.RollbackIncompleteFreeAndNil(DBXTran);
  end;

Will be ok, while:

var
  DBXTran: TDBXTransaction;
begin
  cds2.Open;
  try
    DBXTran := connnection1.BeginTransaction;

    sql1.Close;
    sql1.SQL.Clear;
    sql1.SQL.Text := 'select * from table_one';
    sql1.Open;

    cds2.Append;

    cds2.FieldByName('MyField').AsString := 'test';

    cds2.Post;
    cds2.ApplyUpdates(0);
    connnection1.CommitFreeAndNil(DBXTran);
  finally
    connnection1.RollbackIncompleteFreeAndNil(DBXTran);
  end;

Will give you the error...

DBX Error - ParameterNotSet

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Category: dbExpress
Published on Thursday, 16 September 2010 08:26
Hits: 485

If you tried something like:

with cds1.Params do
begin
  ParamByName('finish').AsDateTime := now;    
  ParamByName('start').AsDateTime := Now-1;  
end;
cds1.Open

And you received error like: DBX Error - ParameterNotSet then don't use AsDateTime, use AsSQLTimeStamp := DateTimeToSQLTimeStamp(Now-1);, so your code should look like:

with cds1.Params do
begin
  ParamByName('finish').AsSQLTimeStamp := DateTimeToSQLTimeStamp(now);    
  ParamByName('start').AsDateTime := DateTimeToSQLTimeStamp(Now-1);  
end;
cds1.Open

PChar vs Pointer.

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Category: dbExpress
Published on Monday, 17 November 2008 11:30
Hits: 474
If you use FillChar on a variable which is type of PChar, you will loose pointer, and FreeMem will not work.

MySQL

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Category: dbExpress
Published on Thursday, 05 November 2009 10:33
Hits: 521

If you added DBXDynalink to your uses list, deployed:

  dbxconnections.ini
  dbxdrivers.ini
  dbexpsda40.dll

Tried everything what is described here.

Then, try also:

  ConnectionName = 'MYSQLCONNECTION'
  DriverName = 'MySQL'
  GetDriverFunc = 'getSQLDriverMYSQL'
  LibraryName = 'dbexpmda.dll'
  VendorLib = 'libmysql.dll'

Exception handling

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Category: dbExpress
Published on Friday, 08 August 2008 07:51
Hits: 785

Problem with dbExpress is that it does not raise an exception if anything is wrong in database (for example, if you try to add primary key which already exist). So, to get an exception, best would be to use OnReconcileError in TClientDataSet... Small example:

 

 procedure Tdm.cdsReconcileError(DataSet: TCustomClientDataSet;
  E: EReconcileError; UpdateKind: TUpdateKind; var Action: TReconcileAction);
begin
  ShowMessage(e.Message);
end;