Creating unique column in .sql script (asp.net core)

Question

CREATE TABLE [User](
   UserId int identity(1,1),
   Email varchar(max) unique not null,
   UserName varchar(30) unique not null,
   [Password] varchar(max)not null,
   PRIMARY KEY(UserId)
);

When I run this script I get an error saying that Email and UserName are of invalid types for unique constraint. So my question is how can I create a unique column in table script?

Answer 1

You cannot set varchar(max) or nvarchar(max) as unique values.. Please consider setting the length of these columns to a lower value.

I think the max length you can use for unique for nvarchars is 450

Passwords and e-mails shouldn't be very long anyway, perhaps 100 length should be more than enough.

Anyway, just dont use max if you want it to be a unique column.

Personally, I think you don't have to enforce passwords to be unique. A user might know if the password is being used by another account if his password is not accepted.