When a new PRIMARY KEY or UNIQUE constraint is added to an existing column, the data in the column or columns must be unique. If duplicate values are found, ALTER TABLE fails. The WITH NOCHECK option ...

A table typically has a column or combination of columns that contain values that uniquely identify each row in the table. This column, or columns, is called the primary key (PK) of the table and ...

Sql constraintsa constraint is a rule or limitation that we place on the data in a database that we can put into a column(s). a constraint is part of the table. we can apply constraints when we create ...

By using cascading referential integrity constraints, you can define the actions that SQL Server 2005 takes when a user tries to delete or update a key to which existing foreign keys point. Skip ...

While used like this, the Column attribute is a convenience, the Key attribute is required -- you have to use it to tell Entity Framework which of your columns corresponds to your table's primary key.