json_build_object（）中的大小写表达式

Question

I want to add a case expression inside of my json_build_object for the times where and endtime has not yet been set.

CODE

Current

SELECT json_build_object(
    'endtime', json_agg(CONCAT(endtime::timestamp::date, ' ', endtime::timestamp(0)::time )), 
    'starttime', json_agg(CONCAT(starttime::timestamp::date, ' ', starttime::timestamp(0)::time )),
    'totaltime', json_agg(starttime::timestamp - endtime::timestamp), 
    )
FROM jobs

Expected

SELECT json_build_object(
    'endtime', json_agg(CONCAT(endtime::timestamp::date, ' ', endtime::timestamp(0)::time )), 
    'starttime', json_agg(CONCAT(starttime::timestamp::date, ' ', starttime::timestamp(0)::time )),
    CASE WHEN endtime IS NULL
        THEN 'totaltime', json_agg(starttime::timestamp - NOW()::timestamp)
        ELSE 'totaltime', json_agg(starttime::timestamp - endtime::timestamp)
    END
    )
FROM jobs

RESULT

Current

{
    "endtime"   : [" ",                    "2019-07-22 18:50:06",     "2019-07-19 19:24:13",   "2019-07-19 16:23:46"], 
    "starttime" : ["2019-07-24 16:02:49",  "2019-07-22 20:12:01",     "2019-07-19 16:55:55",   "2019-07-19 14:56:48"], 
    "totaltime" : [null,                   "01:21:55.150273",         "-02:28:17.795901",      "-01:26:57.872932"]
}

Expected

When the endtime is null I would like like the totaltime to be the time till now

{
    "endtime"   : [" ",                    "2019-07-22 18:50:06",     "2019-07-19 19:24:13",   "2019-07-19 16:23:46"], 
    "starttime" : ["2019-07-24 16:02:49",  "2019-07-22 20:12:01",     "2019-07-19 16:55:55",   "2019-07-19 14:56:48"], 
    "totaltime" : ["01:2..timeTillNow",    "01:21:55.150273",         "-02:28:17.795901",      "-01:26:57.872932"]
}

Answer 1

Because you're using aggregated functions, if you put the case when endtime around the json_agg , you're checking the value of the aggregated endtime and it must be in a group by .

Instead, just like the concat , the case goes inside the json_agg . This expression will be evaluated for each row to provide json_agg with the values to aggregate.

SELECT json_build_object(
    'endtime', json_agg(
        concat(endtime::timestamp::date, ' ', endtime::timestamp(0)::time )
    ), 
    'starttime', json_agg(
        concat(starttime::timestamp::date, ' ', starttime::timestamp(0)::time )
    ),
    'totaltime', json_agg(
        case when endtime is null
            then starttime::timestamp - NOW()::timestamp
            else starttime::timestamp - endtime::timestamp
        end
    )
)
FROM jobs;