Create table of words.

create table words (word varchar2(10))

Create trigger that strips leading and trailing blanks from words before they are inserted into table.

create or replace trigger trim_word  
before insert on words  
for each row  
begin  
  :new.word := trim(:new.word);  
end; 

Insert word with leading and trailing blanks.

insert into words (word) values (' Hello ')

Insert another word with leading and trailing blanks.

insert into words (word) values ('  World  ')

Display words and their lengths.

select word, length(word) from words