Answer
A primary key uniquely identifies each row in a table and cannot be NULL. It ensures uniqueness and is used for indexing and relationships.
Quick Answer
Primary key uniquely identifies each row in a table. Must be unique and NOT NULL. A table can have only one primary key (but it can be a composite of multiple columns). MySQL creates a clustered index on the primary key (InnoDB) - rows are stored in primary key order. Use an integer auto_increment column as primary key for best performance in InnoDB.
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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