FOREIGN_KEY Constraints

• InnoDB supports foreign key constraints.
  • The syntax is:

    [CONSTRAINT symbol] FOREIGN KEY [id] (index_col_name, ...)
    

    [REFERENCES tbl_name (index_col_name, ...)
    

    [ON DELETE {RESTRICT | CASCADE | SET NULL | NO ACTION}]
    

    [ON UPDATE {RESTRICT | CASCADE | SET NULL | NO ACTION}]

• MySQL handles foreign key constraints slightly different than standard SQL.
  • A FOREIGN KEY constraint can reference a non UNIQUE key.
  • InnoDB checks UNIQUE and FOREIGN KEY constraints row-by-row.

How do I add InnoDB data files?

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© 2007 John Michael Pierobon

Notes