I’ve a table data

For the same ER and month, if there’s no data for scenario budget_N or act_N, so no insertion in the final table:

This is what I think a good point to start

select *
FROM your_table
WHERE (ER, MONTH) IN (
    SELECT ER, MONTH
    FROM your_table
    GROUP BY ER, MONTH
    HAVING COUNT(CASE WHEN SCENARIO_CD = 'BUDGET_N' THEN 1 END) = 0
       OR COUNT(CASE WHEN SCENARIO_CD = 'ACT_N' THEN 1 END) = 0
);