------ ORA-01480 error when modifying data: STR bind value at the end of Null characters missing

Recently made a change to a database field value, this value should be more than the number of words previously entered, start time, directly in conventional select PL / SQL Developer with ... for update method changes, but every time the words will be error "ORA-01480: Null characters ending STR bind value of the missing", I thought field length is defined not long enough, but looked at is varchar (2000), I modified fewer than 400 characters , it seems that this is not a problem, and later found on the internet, many students are reproduced almost half are said to be how double quotes, the solution: get rid of half of a double quotation mark, or to each row in plsql left-aligned, so you can remove a lot of space, my God, no more than half a horse double quotes, spaces did not ah. . . , Then I try to modify with update statements, even be friends. . . . It seems sometimes sql statement can not forget it.