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单选题 下列关于自联接的说法中,正确的是( )
学科：数据库应用技术(MySQL8.0+)
时间：2023-05-11 08:30:42
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题目1单选题
有三个表,它们的记录行数分别是10行、2行和6行,三个表进行交叉连接后,结果集中共有()行数据A. 18B. 26C. 不确定D. 120
题目2单选题
组合多条SQL查询语句形成联合查询的操作符是()A. SELECTB. ALLC. LINKD. UNION
题目3单选题
<img src="https://tihai-oss-cloud.itihey.com/img/f81da2388ffe99233aa8c2184916c36a.gif">关系代数练习-学生选课(题干).docx根据附件内容,查询每位学生选修的课程数目,正确的SQL语句是()A. SELECT sName,count(*) FROM student left join sc on student.sNo=sc.sNO GROUP BY sNameB. SELECT sName,count(*) FROM student join sc on student.sNo=sc.sNO GROUP BY sNameC. SELECT sName,count(sc.*) FROM student left JOIN sc on student.sNo=sc.sNO GROUP BY sNameD. SELECT sName,count(sc.scNo) FROM student left JOIN sc on student.sNo=sc.sNO GROUP BY sName
题目4单选题
<img src="https://tihai-oss-cloud.itihey.com/img/f81da2388ffe99233aa8c2184916c36a.gif">关系代数练习-学生选课(题干).docx根据附件内容,联合查询姓名是张三和李四的学生信息,包括uName,uGender,uAge等信息.正确的SQL语句是()A. SELECT sname,sgender,sAge from student where sname='张三' UNION JOIN SELECT sname,sgender,sAge from student where sname='李四'B. SELECT sname,sgender,sAge from student where sname='张三' UNION SELECT sname,sgender,sAge from student where sname='李四'C. SELECT sname,sgender,sAge from student where sname='张三' JOIN SELECT sname,sgender,sAge from student where sname='李四'D. SELECT sname,sgender,sAge from student where sname='张三' and sname='李四'
题目5单选题
下列关于自联接的说法中,正确的是( )A. SQL语句中允许在WHERE短语中为关系定义别名B. 为关系定义别名的格式为:<别名><关系名>C. 在关系的自联接操作中,别名是必不可少的D. 以上说法均正确
题目6单选题
有关系 C(id,name,parent_id),下列选项中能正确找出每个元素的父元素的名称的是( )A. select c1.name,c2.name from course c1 left join course c2 on c1.parent_id = c2.idB. select c1.name,c2.name from course c1 join course c2C. select c1.name,c2.name from course c1 right join course c2 on c1.parent_id = c2.idD. select name,parent_id from course join course on course.parent_id = course.id
题目7多选题
下列连接中,属于SQL连接查询种类的是()A. 内连接B. 中间连接C. 外连接D. 交叉连接
题目8多选题
左外连接是使用下列哪个关键字()A. LEFT JOINB. JOINC. CROSS JOIND. LEFT OUTER JOIN
题目9多选题
<img src="https://tihai-oss-cloud.itihey.com/img/f81da2388ffe99233aa8c2184916c36a.gif">关系代数练习-学生选课(题干).docx根据附件内容,查询张三同学选修的课程名称和对应的成绩,正确的SQL语句是()A. select cName,scGrade from student a join sc b on a.sNO=b.sNO join course c on b.cNO=c.cNO where sName='张三'B. select cName,scGrade from student a join sc b join course c on a.sNO=b.sNO and b.cNO=c.cNO where sName='张三'C. select cName,scGrade from student join sc using(sNO) join course using(cNO) where sName='张三'D. select cName,scGrade from student a JOIN course b JOIN sc c on a.sNo=c.sNO AND b.cno=c.cno WHERE sName='张三'
题目10多选题
<img src="https://tihai-oss-cloud.itihey.com/img/f81da2388ffe99233aa8c2184916c36a.gif">关系代数练习-学生选课(题干).docx 根据附件内容,查询选修了"信息系统"课程的学生学号、姓名和所在院系,正确的SQL语句是()A. SELECT sno,sname,sdept FROM student a JOIN sc b ON a.sno=b.sno JOIN course c ON b.cno=c.cno WHERE cname='信息系统'B. SELECT sno,sname,sdept FROM student a JOIN sc b using(a.sno=b.sno) JOIN course c using(b.cno=c.cno) WHERE cname='信息系统'C. SELECT sno,sname,sdept FROM student JOIN sc using(sno) JOIN course using(cno) WHERE cname='信息系统'D. SELECT sno,sname,sdept FROM student a JOIN course b JOIN sc c ON a.sNo=c.sNO AND b.cno=c.cno WHERE cname='信息系统'
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