Create a new table with the same fields as the existing table.
Insert into the NEW table, using a sub-select from the
original table as the source for the select.
You can also use the Create Table As syntax to create a table which contains data from a select...
Code:
CREATE TABLE mts400_results_NEW AS
Select result_time, epoch, nodeid, parent, voltage * 625/1024 as voltage, humid, humtemp, prtemp, press, taosch0, taosch1, accel_x, accel_y
From mts400_results_1
From a safety viewpoint, I would not try to update the data 'in place.' Create the new table, copy the old data into the new table, processing the voltage as you do so.
Then, after you verify that the voltage data is correct, use the new table as a data source for updating the existing table