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CASCADE dependency 

A table T* is CASCADE dependent on table T if a series of referential CONSTRAINT definitions R1, R2, ..., Rn (n>=1) exist where:

Let R1 and R2 be two different referential CONSTRAINT definitions with the same referencing table S. T1 denotes the referenced table of R1, T2 denotes the referenced table of R2.

If T1 and T2 are identical, or if a table T exists so that T1 and T2 are CASCADE dependent on T, then R1 and R2 must both specify either CASCADE or RESTRICT.

There are different sequences of referential CONSTRAINT definitions that link the tables S and T. A DELETE statement on table T results in an action in table S. In order to ensure that the result of the DELETE statement does not depend on which of the two sequences of referential CONSTRAINT definitions is processed, the above restriction was selected for R1 and R2.

See also:

CASCADE option

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