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A constraint in a table is defined with the INITIALLY IMMEDIATE clause. You executed the ALTER TABLE command with the ENABLE VALIDATE option to enable the constraint that was disabled.
What are the two effects of this command? (Choose two.)
A.It fails if any existing row violates the constraint.
B.It does not validate the existing data in the table.
C.It enables the constraint to be enforced at the end of each transaction.
D.It prevents insert, update, and delete operations on the table while the constraint is in the process of being enabled

INITIALLY IMMEDIATE 表示初始化立即执行，在每条语句执行结束时检验约束
ENABLE VALIDATE 表示原有的和新加的数据都必须遵循约束条件
A 正确，B 错误，ENABLE VALIDATE 会验证已经存在的数据是否违反约束
C 错，INITIALLY DEFERRED 才是事务提交之后检查约束
D 正确，ENABLE VALIDATE 会阻止插入、更新和删除操作来保证数据一致性