给定关系R（A，B，C，D）和S（B，C，E，F）与关系代数表达式π1,5,7（σ2=5（R×S））等价的SQL语句如下：
SELECT（ ）
FROM R，S（ ）；
问题1选项
A.R.A，R.B，S.F
B.R.A，S.B，S.E
C.R.A，S.E，S.F
D.R.A，S.B，S.F
问题2选项
A.WHERE R.B=S.B
B.HAVING R.B=S.B
C.WHERE R.B=S.E
D.HAVING R.B=S.E
正确答案及解析
正确答案
解析
包含此试题的试卷
你可能感兴趣的试题
Advancements in （ ）have contributed to the growth of the automotive industry through the creation and evolution of self-driving vehicles.
-
- A.Artificial Intelligence
- B.Cloud Computing
- C.Internet of Things
- D.Big Data
- 查看答案
In project human resource management , （ ）is not a source of power for the project manager.
-
- A.referent power
- B.expert power
- C.reward power
- D.audit power
- 查看答案
At the project establishment stage , the feasibility study mainly includes techinical feasibility analysis , （ ）, operation environment feasibility analysis and other aspects of feasibility analysis.
-
- A.detail feasibility analysis
- B.opportunity analysis
- C.economic feasibility analysis
- D.risk analysis
- 查看答案
（ ）is a grid that shows the project resources assigned to each work package.
-
- A.Stakeholder engagement assessment matrix
- B.Requirements traceability matrix
- C.Probability and impact matrix
- D.Responsibility assignment matrix
- 查看答案
Xinhua News Agency reported in January 2022，Chian will further promote the developmet of a digital economy during the 14th Five-Year Plan eriod（2021-2025）. The plan also emphasized industrial （ ）transformation.
-
- A.digital
- B.networking
- C.intelligentize
- D.informatization
- 查看答案