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Which three statements correctly describe the functions and use of constraints? （）
A:Constraints provide data independence.
B:Constraints make complex queries easy.
C:Constraints enforce rules at the view level.
D:Constraints enforce rules at the table level.
E:Constraints prevent the deletion of a table if there are dependencies.
F:Constraints prevent the deletion of an index if there are dependencies.

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出自：Oracle认证

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