if make mysql producing blunder #1064

i am attempting run following formula phpmyadmin:

set @tagtokennum=0;
select @tagtokennum:=tag_token_id tag_token where tag_token_name = 'xxx';
delimiter go
if @tagtokennum zero following 
   insert tag_token (tag_token_name) values ('xxx');
   name @tagtokennum:=last_insert_id();
end if;
go

i have also attempted but delimiter matter analogous go. i accept blunder summary "#1064 - have an blunder your sql syntax; check authority corresponds your mysql server chronicle right syntax circuitously 'if @tagtokennum zero following insert tag_token ..."

as distant i tell, i am following repremand syntax statements mysql. i'm many some-more informed microsoft sql, it's wholly illusory i'm doing something wrong. i'd conclude any assistance offer. thanks.
- dave