以下描述正确的是？

Question

A、关系数据库表中记录是不能重复的。

B、关系数据库表的主键上默认建有索引，且是唯一索引。

C、索引需要专门的存储空间进行存放，插入、更新、删除等操作会引起索引维护更新

D、只要条件语句中有索引字段，SQL执行时就一定能够用到索引。

Answer 1

abc

Answer 2

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

Answer 3

ABC