If a Client expression is calling Server expression, will the data be written in database?

We populate the column(UTC_OORDERS) in  Sales_data  through integration interface,

Now, in series setup we have used this client expression, to NULL past records,

1) Will it delete data from database  (for past dates)?

2) will all the data be abolished as we are using client expression and client expression does not store data in databse..
I m confused in this scenario...

kindly help