oracle - EXECUTE IMMEDIATE PL/SQL? -

create or replace trigger p88 after insert on reparation     each row     declare vope number;     begin       select observation_reparation vope repartion;       if(vope null)then    execute immediate 'alter table ' || reparation.observations_reparation || ' modify libelle_piece nvarchar2(50)';     end if; end; / 

i this:

error:table or view not exist.

create or replace trigger p88 after insert on reparation each row declare vope number;  begin    select observation_reparation vope repartion;    if(vope null)then      execute immediate 'alter table reparation rename column observations_reparation libelle_piece';    end if; end; 

if need change declaration of column need alter statement

alter table reparation modify (libelle_piece nvarchar2(50))