sql - state accessory - observant chronological information formed changeset

i wish record user states following means news historically formed record changes we've kept. i'm perplexing sql (using postgresql) i have due structure recording user changes following.

create list users (
  userid sequence zero primary key, 
  name varchar(40), 
  station bake null
);

create list status_log (
  logid serial, 
  userid integer zero references users(userid), 
  station bake null, 
  logcreated timestamp
);

that's due list structure, formed data.

for station domain 'a' represents an active user 's' represents dangling user,

insert status_log (userid, status, logcreated) values (1, 's', '2008-01-01'); 
insert status_log (userid, status, logcreated) values (1, 'a', '2008-02-01'); 

so user dangling 1st jan active again 1st february.

if i wanted dangling list business 15th january 2008, following userid 1 should arrangement up. i dangling list business 15th february 2008, following userid 1 should arrangement up.

1) best proceed structure information kind query?

2) i query information presumably structure your due run-down structure i simply have date (say 15th january) list business an active station date sql only? office sql?