Find the missing record - sql

Question

Three tables are connected to each other in the following manner:
Employee (ID, name) to Salary (ID, Employee_id, Vendor_id, total_amount, date_paid) by employee ID
Salary (ID, Employee_id, Vendor_id) to Vendor (Id, name) by vendor ID
Each employee ID has at least 2 vendors.
However one vendor is same for all employees – “ABC”
I need a list of employees that Vendor ABC was not paid.
For example:
Employee Vendor Month Total_amount
123 ABC Jan 150
123 DEF Jan 200
456 ABC Jan 150
456 XYZ Jan 250
123 DEF Feb 200
456 ABC Feb 150
456 XYZ Feb 250
My result should be Employee_ID 123 for Feb, as Vendor ABC was not paid that month.

Answer 1

SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE table_name ( Employee, Vendor, Month, Total_amount ) AS
SELECT 123, 'ABC', 'Jan', 150 FROM DUAL UNION ALL
SELECT 123, 'DEF', 'Jan', 200 FROM DUAL UNION ALL
SELECT 456, 'ABC', 'Jan', 150 FROM DUAL UNION ALL
SELECT 456, 'XYZ', 'Jan', 250 FROM DUAL UNION ALL
SELECT 123, 'DEF', 'Feb', 200 FROM DUAL UNION ALL
SELECT 456, 'ABC', 'Feb', 150 FROM DUAL UNION ALL
SELECT 456, 'XYZ', 'Feb', 250 FROM DUAL;
Query 1:
WITH EVA( Employee, Vendor, Total_Amount ) AS (
SELECT DISTINCT
Employee,
Vendor,
Total_Amount
FROM table_name
),
Months ( Month ) AS (
SELECT DISTINCT MONTH FROM table_name
)
SELECT Employee, Vendor, Month, Total_Amount
FROM EVA CROSS JOIN Months
MINUS
SELECT Employee, Vendor, Month, Total_Amount
FROM table_name
Results:
| EMPLOYEE | VENDOR | MONTH | TOTAL_AMOUNT |
|----------|--------|-------|--------------|
| 123 | ABC | Feb | 150 |