I only use triggers as a last resort, and this isn't one of them. One technique you can use is to add a column containing a CHECKSUM() of whatever columns should not be updated, and then have a check constraint enforce a condition that the checksum value of these non-updatable columns should be equal to the value of the checksum column.

For example:

create table Customer

(

CustomerID int not null primary key,

CustomerName varchar(80) not null,

CustomerPhone varchar(80) not null,

SalesLeadID int not null,

CustomerCheckSum int not null,

constraint cc_CustomerCheckSum

check (checksum( CustomerID, SalesLeadID ) = CustomerCheckSum)

);

Supply the checksum value when inserting the table:

insert into Customer

values (32, 'John Doe', '555-555-5555', 15, CHECKSUM( 32, 15) );

The columns CustomerName and CustomerPhone can be updated.

update Customer set CustomerPhone = '555-555-1234' where CustomerID = 32;

(1 row(s) affected)

But here we see the result of attempting to update CustomerID or SalesLeadID.

update Customer set SalesLeadID = 20 where CustomerID = 32;

Msg 547, Level 16, State 0, Line 16

The UPDATE statement conflicted with the CHECK constraint "cc_CustomerCheckSum".

Of course the checksum column can also be updated, but it provides at least some degree of deterrent. If the entire record should never be updated, maybe this is a financial application, then you can populate the checksum column using a default constraint and prevent the need to supply checksum value in insert statement.