What are concatenated keys?

Concatenated primary key: Also known as composite primary key is a combination of two or more column values used to define a key in a table. Sometimes a single column does not contain sufficient information to distinguish one record from every other record in the table.

Which table has a concatenated key?

Concatenated Foreign Keys The form table that stores data about the forms that are part of a specific tax return uses the concatenation of the form’s ID and the primary key of the project table for its primary key. A foreign key is the same as the complete primary key of another table.

What is a non primary key?

A non-primary key that can be used to identify only one row in a table. Alternate keys may be used like a primary key in a single-table select. Foreign. A key that has migrated to another entity. At the most basic definition, “a key is a unique identifier”, so unique key is a pleonasm.

Is candidate key a primary key?

Primary key is most important part of any relation or table. Candidate key signifies as which key can be used as Primary Key. Primary Key is a candidate key.

What is a composite key in SQL?

A composite key is made by the combination of two or more columns in a table that can be used to uniquely identify each row in the table when the columns are combined uniqueness of a row is guaranteed, but when it is taken individually it does not guarantee uniqueness, or it can also be understood as a primary key made …

Can a surrogate key be a primary key?

In a current database, the surrogate key can be the primary key, generated by the database management system and not derived from any application data in the database. The only significance of the surrogate key is to act as the primary key.

Can unique key be a primary key?

A primary key must be unique. A unique key does not have to be the primary key – see candidate key. That is, there may be more than one combination of columns on a table that can uniquely identify a row – only one of these can be selected as the primary key.

Is foreign key always primary key?

A foreign key must refer to an entire primary key, and not just part of it. Consider a Department table with a primary key of company_name + department_name. An Employee table should only refer to both attributes and not to department_name alone. Lack of foreign key indexes.

Can foreign key point to a non primary key?

A FOREIGN KEY constraint does not have to be linked only to a PRIMARY KEY constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table. So in your case if you make AnotherID unique, it will be allowed.