Oracle SQL - Assign queue of customers to list of Employees - sql

Question

I need to distribute list of employees to customers.
For example:
Table 1: List of Employees: A, B & C
Table 2: List of Customers: 1, 2, 3, 4, 5, 6, 7, 8, 9
The needed result:
|------------|------------|
| Customers | Employees |
|------------|------------|
| 1 | A |
| 2 | B |
| 3 | C |
| 4 | A |
| 5 | B |
| 6 | C |
| 7 | A |
| 8 | B |
| 9 | C |
|------------|------------|

Answer 1

You can use ROW_NUMBER() to assign a number on the fly to the employees, and the MOD() to do the rolling join. For example:
select
c.id,
e.name
from (
select t.*,
row_number() over(order by name) as rn
from employees t
) e
join customers c on e.rn =
mod(rn, (select count(*) from customers)) + 1

Answer 2

Number all rows, then use a modulo function for the join:
with e as
(
select employee, row_number() over (order by employee) as rn
from employees
)
, c as
(
select customer, row_number() over (order by customer) as rn
from customers
)
select c.customer, e.employee
from c
join e on e.rn - 1 = mod(c.rn - 1, (select count(*) from e))
order by c.customer;
Demo: https://dbfiddle.uk/?rdbms=oracle_18&fiddle=43a6ca7469dff023d5513fa209e33ea7

Answer 3

You can use MOD function for this purpose. Try below code.
CREATE TABLE EMP
AS
SELECT 'A' AS EMP FROM DUAL
UNION ALL
SELECT 'B' AS EMP FROM DUAL
UNION ALL
SELECT 'C' AS EMP FROM DUAL;
CREATE TABLE CUST
AS
SELECT '1' AS CUST FROM DUAL
UNION ALL
SELECT '2' AS CUST FROM DUAL
UNION ALL
SELECT '3' AS CUST FROM DUAL
UNION ALL
SELECT '4' AS CUST FROM DUAL
UNION ALL
SELECT '5' AS CUST FROM DUAL
UNION ALL
SELECT '6' AS CUST FROM DUAL
UNION ALL
SELECT '7' AS CUST FROM DUAL
UNION ALL
SELECT '8' AS CUST FROM DUAL
UNION ALL
SELECT '9' AS CUST FROM DUAL;
SELECT CUST, EMP
FROM (SELECT ROW_NUMBER () OVER (PARTITION BY 1 ORDER BY EMP) AS ID, EMP
FROM EMP) EMP
INNER JOIN CUST ON MOD (TO_NUMBER (CUST.CUST) - 1, 3) = EMP.ID - 1
ORDER BY 1;