Scalar function throws error while using in SQL - sql

Question

My question is:
Write a query to display user name and password. Password should be generated by concatenating first two characters of user name , length of the user name and last three numbers in the phone number and give an alias name as USER_PASSWORD. Sort the results based on the user name in descending order.
select
name,
concat(substring(name, 1, 2), cast(len(name) as varchar), cast(right(phno, 3) as varchar)) as USER_PASSWORD
from
users
order by
name desc;
I get this error:
cast(len(name) as varchar),
ERROR at line 5: ORA-00906: missing left parenthesis
Thanks

Answer 1

You have five issues:
CONCAT only takes two arguments so you either need CONCAT(a, CONCAT(b, c)) or use the || string concatenation operator a || b || c
CAST requires the data type and length CAST(a AS VARCHAR2(10))
SUBSTRING is not an Oracle function, you want SUBSTR;
LEN is not an Oracle function, you want LENGTH;
RIGHT is not an Oracle function, your want SUBSTR with a negative index.
SELECT name,
concat(
substr(name, 1, 2),
concat(
cast(length(name) as varchar2(10)),
cast(SUBSTR(phno, -3) as varchar2(10))
)
) as USER_PASSWORD
from users
order by name desc;
However, you do not need to explicitly use CAST as you can use an implicit conversion between data types:
SELECT name,
substr(name, 1, 2) || length(name) || SUBSTR(phno, -3) as USER_PASSWORD
from users
order by name desc;
Which, for the sample data:
CREATE TABLE users (name, phno) AS
SELECT 'Benny', '0123111' FROM DUAL UNION ALL
SELECT 'Betty', '4567111' FROM DUAL UNION ALL
SELECT 'Beryl', '2222111' FROM DUAL;
Both output:
NAME
USER_PASSWORD
Betty
Be5111
Beryl
Be5111
Benny
Be5111
fiddle
Which leads to the final point, don't generate obvious passwords; generate random or pseudo-random passwords. Then don't store them as plain text; instead store them as a salted-hash.

Answer 2

Concat() is limited to two arguments in Oracle. Use || instead.
with my_data as (
select 'abcdefg' as name, 12345 as phno from dual
)
select
name,
substr(name, 1, 2) ||
length(name) ||
substr(to_char(phno),-3) as user_password
from my_data
| NAME | USER_PASSWORD |
| --------|---------------|
| abcdefg | ab7345 |
fiddle