comparing varchar fields in PL/pgSQL

Hi all,

I try to make a simple triger with PL/pgSQL.

It starts on update and in my table I have a field mname varchar(20).

How can I compare if the new and the old value for this field are the same.

I tryed: if NEW.mname <> OLD.mNAME THEN ....

but it is not working !

Exist any deteilet documentation about the PL/pgSQL.

Many thanks.