Answer
A primary key uniquely identifies each row and automatically creates a unique index for fast lookups.
Quick Answer
Primary key uniquely identifies each row in a table - must be unique and NOT NULL. PostgreSQL automatically creates a unique index on the primary key columns. You can define it inline (id SERIAL PRIMARY KEY) or as a table constraint. Composite primary keys use multiple columns together. The primary key is the main way to reference a row from foreign keys in other tables.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ