# primary key

CEFR C1 · Compound

Source: https://englishreference.com/word/primary-key
Updated: 2026-07-22

## Definition

a unique code or piece of information used to identify one specific record in a database. Just like a passport number identifies one person, this ensures no two rows of data are exactly the same.

For teachers: a specific column or set of columns in a database table that uniquely identifies each row. It must contain unique values and cannot contain null entries, ensuring data integrity and allowing for efficient record retrieval.

## Examples

- The student ID serves as the primary key for the database.
- When designing the customer table, the developer assigned a unique serial number as the primary key to prevent duplicate entries.
- In relational database design, the primary key is essential for establishing relationships with other tables, where it is referenced as a foreign key to maintain referential integrity across the system.

## Usage notes

- Often used in the context of SQL and relational database management systems (RDBMS).

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.