create table entContact(
    id int unsigned NOT NULL auto_increment,
    person varchar(32) NOT NULL,
    primary key(id)
);

insert into entContact(person) values('Joe'), ('Jessica'), ('Alan');

create procedure lstContacts(pPersonMatch varchar(64))
begin
    select * from entContact
    where pPersonMatch is null or person rlike pPersonMatch;
end;


-- Either of these successfully return Joe.
call lstContacts('Joe(seph)?');
select * from entContact where person rlike 'Joe(seph)?';

-- Any of these successfully return an empty set.
call lstContacts('Sarah?');
select * from entContact where person rlike 'Sarah?';
select * from entContact where person rlike null;

-- Successfully returns all Joe, Jessica, and Alan.
select * from entContact where null is null or person rlike null;

-- This one hangs, but should return the same thing as the previous statement.
call lstContacts(null);