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To create a unique constraint, using: sql server management studio. transact-sql. before you begin security permissions. requires alter permission on the table. using sql server management studio to create a unique constraint. in object explorer, right-click the table to which you want to add a unique constraint, and click design.. To modify a unique constraint using: sql server management studio. transact-sql. before you begin security permissions. requires alter permission on the table. using sql server management studio to modify a unique constraint. in the object explorer, right-click the table containing the unique constraint and select design.. The sql server documentation says that a unique constraint automatically creates a unique index to preserve the no-duplicate integrity of the column; but it doesn't say anything about what else is added to the checking of the column by the unique constraint..

Sql create table primary key | cabinets matttroy

Both primary key and unique key enforces the uniqueness of the values (i.e. avoids duplicate values) on the column[s] on which it is defined. also these key’s can uniquely identify each row in database table. [also read] difference between sql server varchar and nvarchar data type below table lists out the major difference between primary key and unique key:. Sql primary key constraint. the primary key constraint uniquely identifies each record in a table. primary keys must contain unique values, and cannot contain null values. a table can have only one primary key, which may consist of single or multiple fields. sql primary key on alter table.. Unique key in sql. a unique key is a set of one or more than one fields/columns of a table that uniquely identify a record in a database table. you can say that it is little like primary key but it can accept only one null value and it cannot have duplicate values..

alter unique key in sql

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