This example assumes
Note: I always start writing such code in a transaction with rollback. Once the result looks ok, I only select/run the parts that are important.
begin transaction
Select HttpAlias from PortalAlias Where HTTPAlias like '2sxc-dnn%'
Select HttpAlias from PortalAlias Where HTTPAlias like '2sexycontent.2dm.2sic%'
Update PortalAlias
Set HttpAlias = Replace(HttpAlias, '2sexycontent.2dm.2sic', '2sxc-dnn961.dnndev.me')
Where HTTPAlias like '2sexycontent.2dm.2sic%'
Select HttpAlias from PortalAlias Where HTTPAlias like '2sxc-dnn%'
rollback transaction