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Exam C2090-600 All Questions

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Exam C2090-600 topic 1 question 5 discussion

Actual exam question from IBM's C2090-600
Question #: 5
Topic #: 1
[All C2090-600 Questions]

Which statement about NOT ENFORCED unique constraints is TRUE?

  • A. NOT ENFORCED unique constraints can not be defined on primary key columns
  • B. The query optimizer will consider a NOT ENFORCED unique constraint when selecting an optimal data access plan
  • C. When attempting to insert data that does not conform to a NOT ENFORCED unique constraint, a warning will be returned
  • D. Storage requirements for a NOT ENFORCED unique constraint are no different than the storage requirements for a similar unique index
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Suggested Answer: A 🗳️
by db2tester at Oct. 9, 2019, 2:27 p.m.

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db2tester
5 years, 1 month ago
The correct answer is B. In DB2® Version 10.5, support is added for NOT ENFORCED primary key and unique constraints. These informational constraints help the query optimizer to select optimal data access plans when index access to the data provides no additional benefit. If you know that the data conforms to these constraints, you can use the NOT ENFORCED capability to help achieve two goals: - Improve performance, primarily in insert, update, and delete operations on the table - Reduce space requirements that are associated with enforcing a primary key or unique constraint Reference : https://www.ibm.com/support/knowledgecenter/en/SSEPGG_10.5.0/com.ibm.db2.luw.wn.doc/doc/c0061153.html
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