题目内容
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A.C. W. Bachman
B.R. Boyce
C.E. F. Codd
D.J. Gray
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更多“The relational data model is proposed by :”相关的问题
A、convoyed
B、surpassed
C、conquered
D、invaded
The speed limit on most major highways in Massachusetts is 55 mph/88 km with some sections, 65 mph/104 km.
While most non-U.S. driver's licenses(驾驶执照) are acceptable, it's best to bring an international driver's license.
State law requires all vehicle occupants to wear seat belts.
When entering a rotary intersection(转弯的路口), yield to any vehicle already in the rotary.
A right run on red at a traffic signal is permitted after coming to a full stop and yielding to pedestrians(行人) and other traffic, unless a "No Turn on Red" sign is posted.
To ensure your safety and that of others on the road, Massachusetts strictly enforces its drunk driving law.
Driving Safety
You'd better bring an【46】license, although non-U.S. licenses are acceptable.
All vehicle occupants need to wear【47】.
Unless a "No Turn on Red" sign is posted, you can turn【48】on【49】signal.
There is a drunk【50】to ensure safety.
A、Select, Project
B、Cartesian-Product, Project
C、Cartesian-Product, Select, Project
D、Cartesian-Product, Select
A、Select, Project, Cartesian-Product
B、Union, Project, Cartesian-Product
C、Select, Rename, Cartesian-Product
D、Set difference, Project, Cartesian-Product
A、There is no order on the rows.
B、There is no order on the columns.
C、Two tuples can be identical in all column values.
D、Multi-valued attributes are not permitted.
A、Entity integrity
B、Referential integrity
C、Check constraint
D、User defined constraint
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