第三章单元测试
下列有关SELECT语句的语法结构中,各子句出现的顺序正确的是哪一个?
若删除关系R上的索引Stusname,下列哪一个语句是正确的?
若删除关系R中的全部元组,下列哪一个语句是正确的?
若查询考试成绩不为空的学生的学号,下列语句哪个是正确的?
若将所有学生的年龄增加1岁,下列哪一个语句是正确的?
A:SELECT—FROM—WHERE—ORDER—GROUP; B: SELECT—FROM—GROUP—WHERE—ORDER; C:SELECT—FROM—GROUP—ORDER—WHERE; D:SELECT—FROM—WHERE—GROUP—ORDER;
答案:SELECT—FROM—WHERE—GROUP—ORDER;
A: DROP INDEX Stusname; B:DELETE INDEX Stusname; C:DROP Stusname FROM R; D:DELETE Stusname FROM R;
A:DELETE FROM R; B: DROP TABLE R; C:DELETE * FROM R; D:DROP * FROM TABLE R;
A:SELECT Sno FROM SC WHERE Grade IS NOT NULL; B:SELECT Sno FROM SC WHERE Grade != 0; C: SELECT Sno FROM SC WHERE Grade >= 0; D:SELECT Sno FROM SC WHERE Grade NOT IS NULL;
A:UPDATE Student.Sage SET Sage = 1+Sage; B: UPDATE Student.Sage SET Sage = Sage + 1; C:UPDATE Student.* FROM Student SET Sage = Sage + 1; D:UPDATE Student SET Sage = Sage + 1;
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