Insert empty string to Oracle database from SQL Server result strange characters -

i have 2 databases oracle (10.2.0.4) , sql server (2008 r2).

when insert data through linked server:

execute( 'begin insert test_table(id,data1,nip) values(?,sysdate,?);  end;',                      '',            ''          ) @ ls_oracle; 

result in test_table as:

id | data1  | nip ----------------- ǧ  |16/07/21|  

empty string convert "ǧ".

how eliminate strange behavior?

for information:

create table "test_table"     (    "id" varchar2(200 byte),      "data1" date,      "nip" varchar2(200 byte)    ) 

you can use workaround. when you'll use variables problem solved

declare @id nvarchar(50) = '' ,@nip nvarchar(50) = '' execute( 'begin insert test_table(id,data1,nip) values(?,sysdate,?);  end;',                  @id,        @nip      ) @ ls_oracle