# Primary key ## Definition(s) ### Context: [[Nexus - Google Analytics Certificate Course|Google Analytics Certificate]] #### Sub-context: [[Relational database]] >[! Definition] >An identifier in a database that references a column in which each value is unique, no blank or null. #### [[Data Integrity]] >[! note] Definition >The value must be unique per column. > ## Examples When a table has no PK, a PK can be created by using multiple columns of the table. SEE [[Composite key]] ## Related [[Relational database]] [[Foreign key]] [[Composite key]] [[Data Integrity]] ## Resources ## Flashcards The below code are generated for use with [Spaced Repetition plugin](https://github.com/st3v3nmw/obsidian-spaced-repetition/) [docs](https://www.stephenmwangi.com/obsidian-spaced-repetition/) An identifier in a database that references a column in which each value is unique, no blank or null. @@@ [[Primary key]]