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From Ali Akhtar <>
Subject Doing a calculation in a query?
Date Mon, 10 Oct 2016 16:08:27 GMT
I have a table for tracking orders. Each order has an `ordered_at` field
(can be a timestamp, or a long with the milliseconds of the timestamp) and
`shipped_at` field (ditto, timestamp or long).

orderd_at tracks when the order was made.

shipped_at tracks when the order was shipped.

When retrieving the orders, I need to calculate an additional field, called
'shipment_delay'. This is simply, 'shipped_at - ordered_at`. I.e how long
it took between when the order was made, and when it was shipped.

The tricky part is, that if an order isn't yet shipped, then it should just
return how many days it has been since the order was made.

E.g, if order was made on Jan 1 and shipped on Jan 5th, shipment_delay = 4
 days (in milliseconds if needed)

If order made on Jan 1, but not yet shipped, and today is Jan 10th, then
shipment_delay = 10 days.

I then need to sort the orders in the order of 'shipment_delay desc', i.e
show the orders which took the longest, at the top.

Is it possible to define 'shipment_delay' at the table or query level, so
it can be used in the 'order by' clause, or if this ordering will have to
be done myself after the data is received?


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