How to replace first n entries in a column with 0N

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Emily Wilson

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Apr 6, 2021, 8:51:51 AMApr 6
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Hi, 
I am running a calculation and I want to replace my first n entries in the row with empty value. How should I do that?
i.e,                  mycol                                     mycol
                --------------------        to              ---------------------
                          a                                              0N
                          b                                              0N
                          c                                               c
                          d                                               d
Thank you so much for your help!
Emily
                -

András Dőtsch

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Apr 6, 2021, 10:15:48 AMApr 6
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update mycol:0N from `mytable where i<n

Andras

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Nick Psaris

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Apr 10, 2021, 3:13:43 PMApr 10
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if you ever need to replace the first two elements 'by sym', for example, depending on 'i' won't help.

one alternative is to explicitly drop the first two elements and append two with null values:
q)t:([]mycol:`a`b`c`d)
q)update (``,2_) mycol from t

careful with this one, because the ',' append operator will be parsed by q-sql if it is not surrounded by parenthesis

another option is to use the '@' amend operator and replace the first two elements with null values
q)update @[;0 1;:;`] mycol from t




Emily Wilson

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Apr 11, 2021, 10:46:24 AMApr 11
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Thank you so much for your help, Nick!
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