calculation in access


I have a column in access that contains a number. I would like to create another column that has the difference of that number from 30. For example if the first column contained the number 17 then the second column would contain the number 13.

thanks for your help
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Use design view on the table to create the new column then use an update query to do the calculation and update the new field.
pls explain with proper example
If this is always the rule then you should not be storing the second value at all.
You can always calculate it whenever you need it.
If you store it there is a fair chance that the two values will get out of synch and no longer add up to 30.

Also, to do this you would have include code in your data entry form to calculate the second value and drop it into a textbox bound to the second field.

You cannot do things like this in the table design.

See attached sample query

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While the query I have shown will do what you ask I agree with Peter57r that what you are suggesting is not usually a good idea
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Microsoft Access

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