BACHELOR OF BUSINESS ADMINISTRATION

Detailed explanation-1: -The primary key is a constraint that recognizes all of the columns in a row as unique. For a constraint to be recognized as a primary key, it must contain unique values throughout the row and none of the values must be NULL. In a table, there can only be one primary key.

Detailed explanation-2: -Unique constraints ensure that the values in a set of columns are unique and not null for all rows in the table. The columns specified in a unique constraint must be defined as NOT NULL. The database manager uses a unique index to enforce the uniqueness of the key during changes to the columns of the unique constraint.

Detailed explanation-3: -A foreign key (FK) is a column or combination of columns that is used to establish and enforce a link between the data in two tables to control the data that can be stored in the foreign key table.

Detailed explanation-4: -If a UNIQUE constraint is added to a column that has duplicated values, the Database Engine returns an error and does not add the constraint. The Database Engine automatically creates a UNIQUE index to enforce the uniqueness requirement of the UNIQUE constraint.