Richard Huxton wrote:
> Michael Avila wrote:
>
>> I have a table which keeps track of the status of members. In the
>> table is
>>
>> member_id int(8)
>> status_code char(1)
>> status_date date
>> KEY member_id (member_id,status_code,status_date)
>>
>>
>> Each member can have multiple records because a record is added each
>> time
>> the status changes but the old record is kept for history.
>>
>> What I want to do is find the latest status for each member.
>
>
> Michael Fuhr has already described on solution, but if you can alter
> the table definition then there might be a neater solution.
>
> Replace "status_date" with "status_expires" and make it a "timestamp
> with time zone". Set the expiry to 'infinity' for the current record
> and you then have a simple select to find the most recent.
>
> If you regularly want to find which record was active on a particular
> time you'll want two columns: valid_from and valid_to. This makes it
> much easier to find a row for a specific date.
There is a standard way :
Select * from memberstatus A where not exists (select * from emberstatus B where B.member_id=A.member_id and
B.status_date >A.status_date)