Employment agencies or executive recruiters are sometimes simply known as “head hunters” and their main job includes searching for the right candidate to fill a vacant position existing in a firm.()

设有课程(课程号，课程名)和选课(学号，课程号，成绩)两个关系，当修改某一课程的课程号时，必须将选课表中对应的课程号值作出相应变动。实现这一完整性约束使用的SQL子句是()。

A、ON UPDATE RESTRICT
B、ON UPDATE CASCADE

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达芬奇以生动严谨的造型和独具特色的线条与色彩的巧妙运用而著称。()

A、错误
B、正确

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