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Henrik Staun Poulsen avatar image
Henrik Staun Poulsen asked

SSIS Derived Column: Round or Floor

I ran into something perculiar in SSIS today.
In a Derived Column package I was trying to truncate a numeric value to an integer, like this (DT_I4)[MyNumericValue] It turns out that this does not do a truncate, but it rounds (up or down) to the nearest integer.
So I had to do this to get it to truncate: (DT_I4)FLOOR([MyNumericValue]) I tried searching for an answer, but was not able to find any.
Now there is an explaination to be found.
ssistruncateroundmathematics
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Pavel Pawlowski avatar image
Pavel Pawlowski answered
Only to be completely correct to really truncate (cut off decimal places) from signed numeric value you have to write following expression: SIGN([MyNumericValue]) * FLOOR(ABS([MyNumericValue])) As single floor function returns the largest integer value, that is less then or equal to the value provided. In case of negative value eg. `FLOOR(-1.34)` will return `-2`.
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Very important point, not to be missed. (This time I only had positive numbers, so I do not have to change anything in my code). But I think it is really naughty of SSIS to do a round. I still read the code as a Truncate, but it is really doing a Cast(round(x,0) as integer). To my immense surprise
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