SQL Interview Questions #18: What is a primary key?

Task 18:

Which of the following statements describe a primary key in SQL?

The primary key can only be the first column in the table.

A primary key is a column (or set of columns) in a relational database table that uniquely identifies each row in that table. No two rows can have the same primary key value.

Primary keys are often used to establish relationships between tables. Foreign keys in other tables can reference the primary key of the related table, allowing you to efficiently retrieve and manipulate data.

The primary key must be a numeric data type.

The primary key ensures the integrity of the data in the database. This ensures that each row in a table has a distinct identifier and can be uniquely referenced from other tables.

Primary keys are always indexed to ensure uniqueness, fast searching, and improved query performance.

Every table in a relational database must have a primary key.

A primary key includes the values of only one column.

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