多项选择题

A. Constraints provide data independence.B. Constraints……

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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