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st: difference between rows
From
"Dougie Elder" <[email protected]>
To
<[email protected]>
Subject
st: difference between rows
Date
Fri, 20 May 2011 23:10:54 +0100
Apologies if this is quite basic, but I've searched everywhere and I cant
find the answer !
I have a pile of drug prescription data.
Each patient has several rows of prescriptions e.g.
Id start_date days missed days
Pt1 10/12/08 21
Pt1 10/01/09 38
Pt1 14/03/09 36
Pt1 15/04/10 36
Pt2 02/05/09 90
Pt2 03/06/10 32
I need to calculate the no of days where no drug was available in each row
of data i.e calculate the difference between 10/12/08 and 10/01/09 and place
the result of ((10/01/09 - 10/12/08)-21 ) at the end of row 1
Obviously only for each pt
Dougie
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