Question

This is a query that I’ve been using:

select serial_number, DAQ.qtag_no, min(TOH.start_time), order_number, DAQ.creation_time, qtag_status, ar_code, pro_foundin, pro_category, root_cause, remark from UNIT U 
left JOIN WORK_ORDER WO ON WO.order_key = U.order_key
left join TRACKED_OBJECT_HISTORY TOH on TOH.tobj_key = U.unit_key
WHERE U.creation_time > '01/01/2012' AND U.creation_time < '07/20/2012'
AND order_number NOT LIKE '[R]%' 
group by serial_number, qtag_no, order_number, DAQ.creation_time, qtag_status, ar_code, pro_foundin, pro_category, root_cause, remark
order by serial_number

Right now I get 3280 results.
In this setup, there are different stations, such as “Assembly,” “Diagnostics,” etc. My goal for the min(TOH.start_time) column is to return the first start time at the Assembly station, but currently it’s returning the first start time at ANY station. However, if I add another WHERE clause to specify the station (TOH.op_name = ‘Assembly’), it limits the number of results (down to 2700). I’d like to keep the 3280 results and instead for units not scanned in to the Assembly station, return NULL for min(TOH.start_time) column. I tried using the case function, but that requires me to include TOH.op_name in the group by clause, which I’m not looking for. Thanks!

Answer 1

You should just be able to add your condition to the left join I think, like this:

select  serial_number, 
    DAQ.qtag_no, 
    min(TOH.start_time), 
    order_number, 
    DAQ.creation_time, 
    qtag_status, 
    ar_code, 
    pro_foundin, 
    pro_category, 
    root_cause, 
    remark 
from UNIT U 
left 
JOIN    WORK_ORDER WO 
    ON  WO.order_key = U.order_key
left 
join    TRACKED_OBJECT_HISTORY TOH 
    on  TOH.tobj_key = U.unit_key
    and TOH.op_name = 'Assembly'
WHERE   U.creation_time > '01/01/2012' AND U.creation_time < '07/20/2012'
AND     order_number NOT LIKE '[R]%' 
group by serial_number, qtag_no, order_number, DAQ.creation_time, qtag_status, ar_code, pro_foundin, pro_category, root_cause, remark
order by serial_number