Getting distinct values

Question

I have a table storing username,login_date. I need to retreive
username and the last login date of all the users. So I issued the
query
select distinct(username),max(login_date) from login_log group by username,login_date;
but the above returns duplicate usernames ..i.e.. the usernames
are repeated..
How to solve this ?
Kai

Answer 1

Hi, Kai,
GROUP BY  username, login_datemeans "make one row of output for each distinct value of *the combination of* username and login_date.
You want just one row pt output for each distinct value of username, without reference to any other column, so don't mention any other column in the GROUP BY clause
{quote:title=KaiS wrote:}{quote}
I have a table storing username,login_date. I need to retreive
username and the last login date of all the users...Do you want the last login date of *all* users, together, or *each* user separately? No doubt, it's very clear to you, but everyone else has to guess. Please post a little sample data (CREATE TABLE and INSERT statements) and the results you want from that data whenever you have a question.
The query below does both; pick either last_all or last_each.
{code}
SELECT     username
,     MAX (MAX (login_date)) OVER ( )     AS last_all
,     MAX (login_date)           AS last_each
FROM     login_log
GROUP BY username, login_date
{code}