how to determine Maximum Month Year and Month

Question

I have a table that stores salary information (SALARY with fields such as NATIONAL_ID, SALYEAR, SALMONTH, SALAMOUNT, DATE_PAID, etc) for employees.

I need to extract data from that table including the last month an employee was paid a salary.

Unfortunately, DATE_PAID column is null for many cases in that table which forces me to think of using a combination of SALYEAR, SALMONTH to determine the highest value.

SALMONTH stores numbers from 1-12 and SALYEAR stores year information ie 2010, 2015, etc.

Answer 1

Using ROW_NUMBER , we can try:

WITH cte AS (
    SELECT t.*, ROW_NUMBER() OVER (PARTITION BY NATIONAL_ID
                                   ORDER BY SALYEAR DESC, SALMONTH DESC) rn
    FROM yourTable t
)

SELECT *
FROM cte
WHERE rn = 1;

The above approach will target the latest record for each NATIONAL_ID , with "latest" being defined as having the most recent month in the most recent year.

Answer 2

select max(to_date(sal_year||to_char(sal_month,'FM00'),'yyyymm'))

should do it. The TO_DATE is really just for completeness if you want a date datatype.

Answer 3

You would need to use COALESCE like this:

SELECT MAX(COALESCE(YEAR(DATE_PAID) * 100 + MONTH(DATE_PAID), SALYEAR * 100 + SALMONTH))
FROM tablename

Answer 4

Use Correlated Sub Query -

with temp as (
    select national_id, 
    max(to_number(to_char(salyear)||lpad(to_char(salmonth),2,'0'))) as max_salmonthyear
    from salary
    group by national_id)
select *
from salary s, temp t
where s.national_id = t.national_id
  and to_number(to_char(salyear)||lpad(to_char(salmonth),2,'0')) = t.max_salmonthyear
order by 1;

Answer 5

Why not just use aggregation?

select nationalid, max(salyear * 100 + salmonth) as salyearmonth
from t
group by nationalid;

If you want to convert the yearmonth to a date:

select nationalid,
       to_date(max(salyear * 100 + salmonth), 'YYYYMM') as salyearmonth
from t
group by nationalid;

This returns the first date of the salary month.