How
You have to update to a variable then select the value of the variable.
update `datatable` set `rate` := @a := (`rate` + 2);
select @a as `index`;
(Note you have to use the funky := operator, which means this is really definitely an assignment operation)
But why do it like this?
This allows you an atomic operation, updating a column, and returning the value at the same time, without using table locking. Apparently the update operation is atomic, so provided the database connection is not shared @a will not be overwritten.
