Add default value to an existing column based on If Then Else sql server 2008

Question

Is it possible to alter an existing column to accept a default value based on another column value?

For Eg:

Create table #Temp
(
    TempId int not n         


        

Answer 1

You can do it via CHECK constraint,

First you will have to create table,

 create table myTemp1(TempId int not null ,TransCode int,ReasonCode int);

and then add the constraint as

create table myTemp1(TempId int not null ,TransCode int,ReasonCode int);

alter table myTemp1
add constraint check_role CHECK(case when (TransCode = 1 AND ReasonCode = NULL)
                                then 99 else ReasonCode end = ReasonCode);

OR like

alter table myTemp1
add constraint check_role CHECK(ReasonCode = (case when (TransCode = 1 AND ReasonCode
                                = NULL) then 99 else ReasonCode end = 1))

demo at http://sqlfiddle.com/#!3/d633a/1