Unique Constraint

Question

How can we apply unique constraint on a column with varchar datatype so that duplicates in the same column are not allowed, like identity card numbers,Debit Cards etc

Answer 1

DDL example:

ALTER TABLE dbo.MyTable
ADD CONSTRAINT UN_MyTable_DebitCardNumber UNIQUE NONCLUSTERED (DebitCardNumber);

 

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Dan Guzman, SQL Server MVP, http://weblogs.sqlteam.com/dang/

Answer 2

In additional, you can create UNIQUE Non clustered index on that column.

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Best Regards, Uri Dimant SQL Server MVP http://dimantdatabasesolutions.blogspot.com/ http://sqlblog.com/blogs/uri_dimant/

Answer 3

In additional, you can create UNIQUE Non clustered index on that column.

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Best Regards, Uri Dimant SQL Server MVP http://dimantdatabasesolutions.blogspot.com/ http://sqlblog.com/blogs/uri_dimant/

Answer 4

Sure, you can add a constraint providing that you don't already have duplicates in this column.

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