On Wed, Mar 21, 2012 at 11:31 AM, wrote:
>
> I'm trying to use sqldf to query for the earliest date of a blood test when
> patients have had multiple tests in a given year. My query looks like this:
>
> test11 <- sqldf("select CHILD_ID, min(SAMP_DATE)
> from lab
>
I'm trying to use sqldf to query for the earliest date of a blood test when
patients have had multiple tests in a given year. My query looks like this:
test11 <- sqldf("select CHILD_ID, min(SAMP_DATE)
from lab
group by CHILD_ID
having extract (ye
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