Question

Say, I have table named ‘member’

    id     name
 ===================
    a      John
    b      Frank

Member have ‘login_activities’

    id     login_time     gol     member
==========================================
    1      2012-10-01      99      a
    2      2012-10-01     125      b
    3      2012-11-01     255      a
    4      2012-11-02     111      b
    5      2012-11-07     101      a

I want to create view that have information about when first time login and last time login of the members and also the ‘gol’ value only from the last login.

Is it possible?

I’ve tried many ways. One of my attempt:

CREATE VIEW   view_firstlast
     AS
          SELECT
               MIN(a.login_time) as first_login,
               MAX(a.login_time) as last_login,
               a.gol,
               b.name
          FROM
               login_activities a
                   JOIN member b ON a.member = b.id
          GROUP BY
               a.member

It does’nt get right result. The ‘gol’ value is from the first login.
How to do this?

---

Something important here: MySQL doesn’t allow subquery in create view

Answer 1

You are ALMOST there. You have the login times, but I would take it and get the last login ID too to simplify a re-join to the login activities table vs trying to do a join on user AND date/time field since I would expect a key on the primary key of ID and not necessarily on (member, login_time) — however, for this query using the min/max on date grouped by member, I would DEFINITELY have an index on (member, login_time) for optimization.

SELECT
      m.Name,
      PreQuery.First_Login,
      PreQuery.Last_Login,
      LA2.GOL
   from
      ( select
              LA.member,
              MIN(LA.login_time) as first_login,
              MAX(LA.login_time) as last_login,
              MAX(LA.ID) as LastLoginID
          FROM
              login_activities LA
          group by
              LA.member ) PreQuery
        JOIN member M
           ON PreQuery.member = M.id
        JOIN login_activities LA2
           ON PreQuery.LastLoginID = LA2.id

Then, since the above works, but fails due to how MySQL implements views, you might need to do it with TWO views, such that

create view MemberFirstLastOnly
as 
select
      LA.member,
      MIN(LA.login_time) as first_login,
      MAX(LA.login_time) as last_login,
      MAX(LA.ID) as LastLoginID
   FROM
      login_activities LA
   group by
      LA.member

then another

create view MemberLastFirstFinal
as
    SELECT
          m.Name,
          MFLO.First_Login,
          MFLO.Last_Login,
          LA2.GOL
       from
          MemberFirstLastOnly MFLO
            JOIN member M
               ON PreQuery.member = M.id
            JOIN login_activities LA2
               ON PreQuery.LastLoginID = LA2.id