MYSQL：在单个语句中选择多个if（field ='x'max（time）/ if（field ='y'min（time））值

Question

I am trying to get the below select statement to work. Essentially I am trying to get a single row per agent & date that contains the min(time) where agent-state = 'Logged-in', the max(time) where agent-state = 'Logout', the timediff(max(time),min(time)) and the sum(duration) where agent-state = 'Ready'.

My current SQL statement is not complete to this, as I started with just getting the correct min/max time values and hit a wall. As it sits now, the Logged-in min time is returned, but not the logout max time.

AGENT, DATE,         TIME,      DURATION,   AGENT_STATE
Alex, 2013-01-01,   07:25:37,   00:00:00,   Logged-in
Alex, 2013-01-01,   07:26:01,   00:24:48,   Ready
Alex, 2013-01-01,   07:54:20,   00:21:47,   Ready
Alex, 2013-01-01,   08:28:11,   00:03:00,   Ready
Alex, 2013-01-01,   08:34:11,   00:06:29,   Ready
Alex, 2013-01-01,   08:44:30,   00:05:14,   Ready
Alex, 2013-01-01,   08:53:29,   00:06:52,   Ready
Alex, 2013-01-01,   09:03:48,   00:12:13,   Ready
Alex, 2013-01-01,   09:31:56,   00:36:44,   Ready
Alex, 2013-01-01,   09:32:27,   14:58:51,   Logout
Alex, 2013-01-01,   10:11:37,   00:00:00,   Logged-in
Alex, 2013-01-01,   10:12:26,   00:54:44,   Ready
Alex, 2013-01-01,   11:09:28,   00:47:48,   Ready
Alex, 2013-01-01,   11:57:33,   00:16:54,   Ready
Alex, 2013-01-01,   12:15:15,   00:17:32,   Ready
Alex, 2013-01-01,   12:34:44,   00:13:32,   Ready
Alex, 2013-01-01,   12:51:04,   00:16:44,   Ready
Alex, 2013-01-01,   13:12:36,   00:31:38,   Ready
Alex, 2013-01-01,   13:49:46,   00:39:14,   Ready
Alex, 2013-01-01,   14:31:42,   00:28:45,   Ready
Alex, 2013-01-01,   15:00:27,   14:58:51,   Logout

SQL Statement:

select
 `agent`,
 `date`,
 if(`agent_state` = 'Logged-in', min(`time`), null) as `min_login`,
 if(`agent_state` = 'Logout', max(`time`),null) as `max_logout`
from
 t_cisco_agent_state_details
group by
 `agent`, `date`
order by
 `agent`, `date`, `time` asc;

Thanks for any assistance or advice.

Jim

Answer 1

You can't do it this way. The reason you're getting a null for the "other" column is because that agent_state doesn't exist when you group by agent and date. If you add the agent_state to the group-by you'll get 3 rows per agent/date. This isn't quite what you want.

You need a subquery or a couple self-joins. Try something like this:

SELECT agent,
       date,
       MIN(dur)                       AS total_duration,
       TIMEDIFF(MIN(maxt), MIN(mint)) AS time_difference_between_login_and_out,
       MIN(maxt)                      AS logout_time,
       MIN(mint)                      AS login_time
FROM   (SELECT agent,
               date,
               IF(agent_state = 'Ready', SUM(time), NULL)     AS dur,
               IF(agent_state = 'Logged-in', MIN(time), NULL) AS mint,
               IF(agent_state = 'Logout', MAX(time), NULL)    AS maxt,
               agent_state
        FROM   t_cisco_agent_state_details
        GROUP  BY agent,
                  date,
                  agent_state) AS subq
GROUP  BY agent,
          date 

The subquery creates a single row per agent-state, agent and date. Then you can pull your times out of that with the outer query which groups by just agent and date.