SQL Update to flip sign of a value?

Question

Someone entered a ton of numeric data into a table with the sign backwards.

Is there a clean way to flip the sign in the numeric column with a SQL statement?

Answer 1

update my_table
  set amount = -amount
  where <whatever>

Answer 2

It should be straightforward.

update table set column = -column;

Answer 3

UPDATE [table] SET [column]=[column]*(-1)

You can add a WHERE clause as needed to limit which rows you are flipping signs on.

Answer 4

UPDATE MyTable
SET amount = -amount
WHERE amount = ABS(amount)

By including the amount = ABS(amount) clause you prevent unnecessary log activity and index maintenance. It's always a good idea to only update the rows that actually need it.