make record unique in sql server 2012

In SQL server 2012, how do you make the record unique (something like in Access : Indexed - No duplicates) ? I click on the table - select design - but I am unsure what to do next.
Now, field is nvarchar(5) type .. How do you index it so no duplicates are allowed? uniqueidentifier ?  what does AllowNull stand for ? user must enter a value i.e field cant be empty?
Since I imported my table from access, I used to have ID autoinc field. Now in server it says its an int. is it still an autoinc field or something else ?
LVL 22
senadAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Pratima PharandeCommented:
you can use SQL UNIQUE Constraint in SQl server
refer
http://www.w3schools.com/sql/sql_unique.asp

also  ID that you hvae conevrted from access you need to give primary key set identity to increment by 1
refer
http://www.w3schools.com/sql/sql_primarykey.asp
Harish VargheseProject LeaderCommented:
In case you want to achieve this in design mode only, then follow below steps:

Defining unique keys/indexes:

1. Right click on a table and selct "Design" to open the table in design view.
2. Right click anywhere in the design view and select "Indexes/Keys".
3. In the "Indexes/Keys" window opened, click on Add button to add a new index.
4. On the right hand side, choose the column(s) you want to include in the index/unique key.
5. Choose Type as either Index or Unique Key as required.

Defining Auto increment:
In the table design view, select the column to be made Identity (autoincrement), and in the properties box below, expand "Identity Specification" and choose Yes against "(Is Identity)" property.

Thanks,
Harish

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
senadAuthor Commented:
autoinc field - tried saving but changes is not permitted ?
Anthony PerkinsCommented:
>>autoinc field - tried saving but changes is not permitted ?<<
That is because you are rebuilding the table and you have not allowed that to happen: You have the "Prevent saving changes that require table re-creation" setting in Tools | Options set to false.
senadAuthor Commented:
deleted and recreated the field. works ok ...
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft SQL Server

From novice to tech pro — start learning today.