Access SQL query: find the row with the most recent date for each distinct entry in a table

Question

All,

I\'m sure this is a pretty simple SQL query question, but I\'m sure there\'s a good way, and a very BAD way, to do this. Left to my own devices, I\'m liable to end

Answer 1

I think what you're looking for is this:

select id, value, as_of from table_name where as_of = max(as_of) group by id

This says for each id, find the max as_of, and get that value.

This is generic sql. I'm not sure about access. I'm sure if this doesn't work there is something similar.

Good luck! Joe

Answer 2

Not sure what platform you're looking to do this on, but in T-SQL you can do the following:

SELECT t.*
FROM (
    SELECT ID, MAX(As_Of) as r1
    FROM myTable
    GROUP BY ID
    ) as dt
INNER JOIN myTable t ON dt.ID = t.ID and dt.r1 = t.As_Of

Good luck!

EDIT: Well my poor answer was bothering me so i've fixed it, even though this answer already exists elsewhere on the page now.

Answer 3

If you need both the date and the value, you need to do a join:

SELECT ID, Value,As_of 
from yourTable a inner join 
          (SELECT ID, MAX(As_of) as As_of 
          from yourTable group by ID) b 
on a.ID=b.ID and a.As_of = b.As_of

Answer 4

@Funka, that will not work if you have duplicate "value" values for different ID's - that will basically give you a grouped list by "value", not by id...

@Joe Fair, aggregates aren't allowed in where clauses without a subquery/having combo as well, at least not in ANSI...

This will give you the list, but will give duplicates as well if you have multiple rows with the same id/As_of values:

select  t1.id, t1.value, t1.As_of
from    tableName t1
join    (
        select  id as id, max(As_of) as max_as_of
        from    tableName
        group by id
    ) t2
on      t1.id = t2.id
and     t1.As_of = t2.max_as_of

If you want to remove duplicates from that, you'd just want to add a distinct to the top select, like this:

select  distinct t1.id, t1.value, t1.As_of
from    tableName t1
join    (
        select  id as id, max(As_of) as max_as_of
        from    tableName
        group by id
    ) t2
on      t1.id = t2.id
and     t1.As_of = t2.max_as_of

Answer 5

Try something like this

SELECT t1.*
FROM (SELECT Table1.ID, Max(Table1.As_Of) AS MaxOfAs_Of
FROM Table1
GROUP BY Table1.ID
)  AS MaxIDS INNER JOIN Table1 t1 ON MaxIDS.ID = t1.ID
and MaxIDS.MaxOfAs_Of = t1.As_Of