Minimum value of a column corresponding to another column value

Question

I have this data table below that I am pulling from a data base

  type   week  amount
    a   201304  77
    a   201304  77
    a   201304  77
    a   201304  77
    a   201304  71
    a   201304  71
    a   201305  77
    a   201305  77
    a   201305  77
    a   201305  77
    a   201305  77
    a   201305  77

I am trying to pull only the minimum value from the amount column for every week only, so that table should be like this

  type   week  amount
    a   201304  71
    a   201305  77

Thank you for you help

Answer 1

What's wrong with this regular GROUP BY ?

SELECT type, week, MIN(amount) amount
FROM table_name
GROUP BY type, week

EDIT

If you have different types in the same week with the same amount, what do you want to do? If you want to know what type has the MIN(amount) in a week:

SELECT DISTINCT t2.*
FROM
 (SELECT week, MIN(amount) amount
    FROM table_name
    GROUP BY week) t1
  JOIN table_name t2 ON t1.amount = t2. amount AND t1.week = t2.week

Answer 2

Try

Select type, week, amount 
from
    (Select type, week, amount, row_number () over(partition by week, amount order by amount asc) as rownumber
     from table_name)
where rownumber = 1

What this does is assign row numbers to your partition of just week and amount. You may have many amounts per week. This numbers them and you sort them so that the smallest will be on top (row 1). You get just this row in the where clause. This will produce a minimum amount per week regardless of type.

Answer 3

You can use a min and in clause

 select * from my_table 
 where (amount, week ) in (
    select min(amount), week from my_table group by week 
 );