Selecting words that end in 'n' in oracle sqlplus - sql

Question

Select first names and last names of the table teachers where first names end in 'n'.
I wrote:
select first_name, last_name
from teachers
where type='teacher'
and last_name like '%n';
Unfortunately it selects no rows. It should select at least two.
The problem is with " last_name like '%n' " and I can't find a solution. Does anyone have any idea how i can solve this?Screenshot

Answer 1

The thing is, in your example there are no first_name columns that end with n. Yep.
Why? The the column type of first_name is CHAR instead of VARCHAR2, so Oracle fills up the column with spaces when each first name is shorter than 10 characters.
Solutions?
Use VARCHAR2 instead of CHAR as in:
create table teacher (
last_name varchar2(10), -- VARCHAR2 now!
first_name varchar2(10), -- VARCHAR2 now!
type varchar2(10)
);
With this structure your query will run well.
Alternatively, if you don't want to change the table structure, you can TRIM() the column, as in:
select first_name, last_name
from teachers
where type='teacher'
and trim(first_name) like '%n'; -- use TRIM here!

Answer 2

Try using. This will eliminate the chances of leftout of Case sensitive Data.
select first_name, last_name from teachers where lower(type)='teacher' and lower(first_name ) like '%n';

Answer 3

as per the screenshot the first_name, last_name columns have datatype as CHAR.
the thing about CHAR is that is appends spaces to reach its full length.
Example: for first_name CHAR(10) if u store 'Andra' it will be stored as 'Andra '
so use the trim function:
select first_name, last_name
from teachers
where type='teacher'
and trim(first_name) like '%n';
alternatively use the VARCHAR2 datatype instead of CHAR.
it does not append spaces at the end to reach its full length.

Answer 4

As you were told, your query should work. Problem is probably trivial (does case matters? Are there really lower case "n" letters in those names?).
Meanwhile, a few options for you:
SQL> select ename from emp
2 where ename like '%N';
ENAME
----------
ALLEN
MARTIN
SQL> select ename from emp
2 where substr(ename, -1) = 'N';
ENAME
----------
ALLEN
MARTIN
SQL> select ename from emp
2 where regexp_like(ename, 'N$');
ENAME
----------
ALLEN
MARTIN
SQL>
[EDIT: CHAR datatype issue]
SQL> create table empc (ename char(10));
Table created.
SQL> insert into empc select ename from emp;
12 rows created.
SQL> select ename from empc where ename like '%N';
no rows selected
SQL> select ename from empc where trim(ename) like '%N';
ENAME
----------
ALLEN
MARTIN
SQL>

Answer 5

If you have char data type then you should try trimming of space chars from your first_name values
select first_name, last_name
from teachers
where type='teacher'
and trim(first_name) like '%n';
anyway in your screeshot you have not teacher with firt_name endig with n ..try
select first_name, last_name
from teachers
where trim(first_name) like '%n';

Answer 6

You could try something like
SELECT *
FROM teachers a
WHERE TRIM (LOWER (a.first_name)) LIKE '%n';