Sql error please help me on this topic

Question

iam getting a error while alter the existing table to set a primary key
alter table cust_details
add constraint pcode primary key(party_code);iam getting this error
Server: Msg 8111, Level 16, State 1, Line 1
Cannot define PRIMARY KEY constraint on nullable column in table 'cust_details'.
Server: Msg 1750, Level 16, State 1, Line 1
Could not create constraint. See previous errors.

Answer 1

you can use the add constraint , first add not null , then add primary key
otherwise drop the column and add with primary key constraint
alter table cust_details
add constraint not_null_code not null(party_code);