题目内容
为存在的成绩表(学号,课程号,成绩)定义 CHECK约束要求成绩的范围为0-100。sql语言实现为:ALTER TABLE 成绩ADD CONSTRAINT ck_cj CHECK(成绩>=0 and 成绩<=100)
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删除成绩表中的CHECK约束,sql实现语言是: ALTER 成绩DROP CONSTRAINT ck_cj
用户定义完整性约束有以下几种:NOT NULL、CHECK、DEFAULT和 UNIQUE等约束。
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[音频]The term, friend, ______ a wide range of meanings. It can be a nodding acquaintance, a comrade, a confidant, a partner, a playmate, a brother, an ________, etc. As life is full of strife and ________, we need friends to support and help us out of difficulties.
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