Answer
Foreign keys enforce referential integrity using actions like CASCADE, RESTRICT, and SET NULL for parent-child relationships.
Quick Answer
InnoDB foreign key on DELETE: CASCADE (delete child rows too), SET NULL (set FK to NULL), RESTRICT/NO ACTION (block delete if children exist - default). On UPDATE: CASCADE (update FK in children), SET NULL, RESTRICT. MySQL checks FK constraints on every DELETE and UPDATE of parent rows. Add an index on the FK column in the child table - MySQL requires it for performance.
S
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