How can I set up a unique constraint in SQL Server?

In SQL Server, you can utilize the UNIQUE constraint to enforce uniqueness. This constraint ensures that the values in a specific column or columns in a table are unique.

Here is the syntax for creating a unique constraint in SQL Server:

ALTER TABLE table_name
ADD CONSTRAINT constraint_name UNIQUE (column1, column2, ...)

In this context, table_name refers to the name of the table where the constraint is to be added, constraint_name is the name of the constraint, and column1, column2, etc. are the column names where the unique constraint is to be added.

For example, to create a unique constraint on the “id” column in the “students” table, you can use the following syntax:

ALTER TABLE students
ADD CONSTRAINT uq_students_id UNIQUE (id)

This will create a unique constraint named “uq_students_id” on the “id” column.

Before creating a unique constraint, make sure there are no duplicate values in the column to which the constraint is being added, as the unique constraint will not be able to be added.