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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 ?
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senad
Asked:
senad
3 Solutions
 
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
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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
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senadAuthor Commented:
autoinc field - tried saving but changes is not permitted ?
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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.
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senadAuthor Commented:
deleted and recreated the field. works ok ...
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