I remember an example where reads in a transaction then writing back the data is not safe because another transaction may read/write to it in the time between. So i would like to check the date and prevent the row from being modified or read until my transaction is finish. Would this do the trick? and are there any sql variants that this will not work on?

update tbl set id=id where date>expire_date and id=@id

Note: date>expire_date happens to be my condition. It could be anything. Would this prevent other transaction from reading the row until i commit or rollback?