Error: "SQLConnection: there is no active transaction"

[jmlifi]

SQlQuery:

Código Delphi [-]
with tblPzFact,Sql do begin
    Add('select n_fact, nRectif, pzfact.ref_n, pedido, qp, precio, importe, orden,');
    Add('piezas.ref_c,piezas.c_vr,piezas.ref_c||"    "||piezas.c_vr refversion');
    Add('from ' + Principal.FichPzFact + ' pzFact');
    Add('inner join piezas on pzfact.ref_n=piezas.ref_n');
    Add('where pzFact.n_fact= :n_fact');
    ParamByName('N_Fact').AsInteger := NumFact;
    PzFact.Open;
  end;

SQLConnection=TSQLConnectionA

DataSetProvider:
dataset=SQLQuery

ClientDataset:
prProviderName=DataSetProvider