how to get the length of the string in sqlcl - oracle

Question

i am trying to display the top three rows based on their length of the string in names.but the system just reads the predefined length of the string column not the string in the column
SQL> select max(length(name)) from cus_detail;
MAX(LENGTH(NAME))
-----------------
10
SQL> select *
from (select id, name, length(name) as namelen, distance
from cus_detail
order by length(name) desc
)
where rownum<=3;
ID NAME NAMELEN DISTANCE
---------- ---------- ---------- ----------
1 paul 10 15
2 baul 10 15
3 mereum 10 20

Answer 1

That's what CHAR datatype does - it right-pads value with spaces up to the full column length:
SQL> create table test (name char(10));
Table created.
SQL> insert into test (name) values ('London');
1 row created.
SQL> select max(length(name)) from test;
MAX(LENGTH(NAME))
-----------------
10
SQL>
A closer look:
SQL> select '#' || name ||'#' name, dump(name) dmp from test;
NAME DMP
------------ --------------------------------------------------
#London # Typ=96 Len=10: 76,111,110,100,111,110,32,32,32,32
^^^^ L o n d o n ^^^^^^^^^^^
spaces spaces
So, you could trim the value:
SQL> select max(length(trim(name))) from test;
MAX(LENGTH(TRIM(NAME)))
-----------------------
6
SQL>
or - even better - change column's datatype to varchar2.