Uderstanding DECODE and ENCODE in MYSQL - mysql

Question

I needed to save id in such a way that would make it encrypted and so that it would take up exactly 8 characters.
I did that using the following command:
SELECT encode(LPAD(id,4,0),'abc')
This command turns an id = 1
into 0001 and then turns that into a code fe5ab21a
How do I decrypt this code?
Below is an example of a select and the result it generates
SELECT 0001
, DECODE(ENCODE('0001', 'abc'), 'abc')
, UNHEX(DECODE(ENCODE('0001', 'abc'), 'abc'))
, ENCODE('0001','abc')
, DECODE('fe5ab21a', 'abc')
, UNHEX(DECODE('fe5ab21a', 'abc'))
, HEX('0001')
The result:
1
30303031
0001
fe5ab21a
68d357a7005dcbe0
NULL
30303031

Answer 1

As I understand, you want to make like a short unique key-pass that's linked to one of your ID.
Be careful with this kind of encryption, if someone want to break it, it'll take less than a few minutes, it's really weak. But if it's only for some obfuscation without security risk, it's ok.
To improve a bit the security (but decrease the user experience), try to use AES_ENCRYPT()
The wrong thing with your code is that you don't force the type of input/output, here is something with the proper typing.
SQL Fiddle
MySQL 5.6 Schema Setup:
CREATE TABLE t
(`id` int, `name` varchar(7))
;
INSERT INTO t
(`id`, `name`)
VALUES
(1, 'hello'),
(2, 'hola'),
(3, 'bonjour')
;
Query 1:
select *, ENCODE(id,'KEY') as encrypted_id from t
Results:
| id | name | encrypted_id |
|----|---------|--------------|
| 1 | hello | Vw== |
| 2 | hola | yw== |
| 3 | bonjour | iA== |
Query 2:
SELECT * from t where id = CAST(DECODE(FROM_BASE64('yw=='),'KEY') AS CHAR(50))
Results:
| id | name |
|----|------|
| 2 | hola |