How do I create a multiple column unique constraint in SQL Server

Question

I have a table that contains, for example, two fields that I want to make unique within the database. For example:

create table Subscriber (
    ID int not null         


        

Answer 1

I assume that only way to enter data into that table is through SPs, If that's the case you can implement some logic in your insert and update SPs to find if the values you are going to insert / update is already exists in that table or not.

Something like this

create proc spInsert
(
    @DataSetId int,
    @Email nvarchar(100)
)
as
begin

if exists (select * from tabaleName where DataSetId = @DataSetId and Email = @Email)
    select -1 -- Duplicacy flag
else
begin
    -- insert logic here
    select 1 -- success flag
end

end
GO


create proc spUpdate
(
   @ID int,
   @DataSetId int,
   @Email nvarchar(100)
)
as
begin

if exists 
(select * from tabaleName where DataSetId = @DataSetId and Email = @Email and ID <> @ID)
    select -1 -- Duplicacy flag
else
begin
    -- insert logic here
    select 1 -- success flag
end

end
GO