请问:查询1号课比2号课成绩高的学生的学号的正确SQL语句是()。(选择一项) a) select sl.sno from (select sno,score from sc where cno=1) as sl,( selectsno,score from sc where cno=2) as s2 where s1.sno=s2.sno; b) select s1.sno from (select sno,score from sc where cno=1) as s1,( selectsno,score from scwhere cno=2)as s2where s1.sno=s2.sno ands1.score>s2.score; c) select s1.sno from (select sno,score from sc where cno=1) as s1,( selectsno,score from sc where cno=2) as s2 where s1.score>s2.score; d) select s1.sno from (select sno,score from sc ) as s1,( select sno,score from sc )as s2 where s1.sno=s2.sno and s1.score>s2.score;
时间: 2024-04-19 12:29:31 浏览: 116
表示学生对象,包含姓名和成绩属性。使用`ArrayList`来存储学生对象,实现了添加学生、显示所有学生、计算平均成绩、查找学生等功能。提供了菜单选项,b) select s1.sno from (select sno,score from sc where cno=1) as s1, (select sno,s允许用户选择不同的操作,直到选择退出程序为止。
相关问题
现有一个student表包含姓名,学号,一个sc表包含学号,成绩,课号,用sql语句检索“001”号课成绩比“003”号课成绩高的所有学生的学号、姓名、001号课程成绩和002号课程成绩及成绩差
你可以使用SQL的JOIN和条件查询来完成这个任务。假设`student`表名为`T_student`,`sc`表名为`T_sc`,并且`student`表中的主键为`sid`(学生ID),`sc`表中的关联字段为`sno`(学号)。下面是一个示例的SQL语句:
```sql
SELECT T_student.sid, T_student.name,
T_sc.score AS score_001,
COALESCE(T_sc.score_002, 0) AS score_002,
(COALESCE(T_sc.score_001, 0) - COALESCE(T_sc.score_003, 0)) AS score_difference
FROM T_student
LEFT JOIN (
SELECT sno, '001' as course_code, score as score_001
FROM T_sc
WHERE course_code = '001'
) sc1 ON T_student.sid = sc1.sno
LEFT JOIN (
SELECT sno, '002' as course_code, score as score_002
FROM T_sc
WHERE course_code = '002'
) sc2 ON T_student.sid = sc2.sno
LEFT JOIN (
SELECT sno, '003' as course_code, score as score_003
FROM T_sc
WHERE course_code = '003'
) sc3 ON T_student.sid = sc3.sno
WHERE T_sc1.score > T_sc3.score;
```
这个查询首先通过LEFT JOIN将学生表与每门课程的成绩表连接起来,并获取了学生001号和002号课程的成绩。然后筛选出001号成绩大于003号的成绩的学生。如果某个学生没有某门课程的成绩,`COALESCE`函数会返回0。
现有一个student表包含姓名,学号,一个sc表包含学号,成绩,课号,用sql语句使用多表联合(不用join语句)检索“001”号课成绩比“003”号课成绩高的所有学生的学号、姓名、001号课程成绩和002号课程成绩及成绩差
你可以使用子查询和条件运算符来完成这个任务,虽然这不是标准的SQL join语句,但在某些数据库系统中可以实现类似的效果。假设`student`表名为`s`,`sc`表名为`t`,下面是一个示例SQL语句:
```sql
SELECT s.学号, s.姓名, t1.成绩 AS 成绩_001, t2.成绩 AS 成绩_002,
(t1.成绩 - COALESCE(t2.成绩, 0)) AS 成绩差
FROM (
SELECT 学号, MAX(成绩) AS 最高成绩
FROM sc
WHERE 课号 = '001'
GROUP BY 学号
) AS t1
LEFT JOIN sc t2 ON t1.学号 = t2.学号 AND t2.课号 = '002'
LEFT JOIN student s ON s.学号 = t1.学号
WHERE t1.最高成绩 > (
SELECT MAX(成绩)
FROM sc
WHERE 课号 = '003'
AND s.学号 = t1.学号
)
```
这个查询首先找出每个学生在'001'号课的最高成绩(子查询t1),然后通过LEFT JOIN获取他们对应的'002'号课的成绩以及学生的姓名。最后的WHERE子句筛选出'001'号课成绩高于'003'号课的学生。
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