A primary unique key:

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BlackTom AI · Accepted Answer

In this question about a primary unique key, we evaluate what a primary key is supposed to do in a relational table.
Option 1: 'Identifies a single row.' This is accurate because a primary key uniquely identifies each row in the table, ensuring that no two rows share the same key value and that the row can be retrieved unambiguously.
Option 2: 'Must always be composed of two or more columns.' This is incorrect. While a composite (multi-column) primary key is possible, a primary key is not required to be multi-column; many tables use a single-column primary key (a simple key such as an ID), so requiring two or more columns is false.
Option 3: 'Identifies a single column.' This is misleading. A primary key identifies a row, not a single column. A single column can be a primary key, but the key’s defining property is row-level uniqueness, not column-level identification.
Option 4: 'Can only contain one column.' This is false as well because primary keys can be composite, meaning they can consist of multiple columns grouped together to enforce uniqueness across rows when a single column cannot.

A primary unique key:

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Question at position 11 In ERDs, the primary key isAn attribute that cannot be modified after it is setAn attribute that uniquely identifies each record in a database tableA graphical symbol indicating the connection between entitiesA set of optional attributes linked to an entity

A database table usually has a(n) _______________________ that uniquely identifies each row in the table.

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