Question

My database consists of an entry about once per a month for a number of individuals, identified by ID. Dates are stored in fields titled YEAR and WEEK. I have a binary flag, called BINARY_FLAG. I would like to grab the last week for each individual in a specifc year where the binary flag was on.

My code to pull the initial data is as follows:

select ID, year, week, binary_flag
from my_table
where year = 2000 and
binary_flag = 1

This will return all entries for year 2000 where binary flag is 1. However, there will be multiple entries for many of the individuals, if the binary flag was 1 for numerous weeks. How do I remove all but the last week?

Answer 1

select * from my_table t1
join 
(select ID, year, max(week) maxWeek
from my_table
where year = 2000 and
binary_flag = 1
group by Id,year) t2
on
(t1.Id=t2.id) and (t1.year=t2.year) and (t1.week=t2.maxWeek)