select a.* ,b.s_score as 01_score,c.s_score as 02_score from student a join score b on a.s_id=b.s_id and b.c_id='01' left join score c on a.s_id=c.s_id and c.c_id='02' or c.c_id = NULL where b.s_score>c.s_score

这是一个 SQL 查询语句，其目的是从两个表中选择学生信息和分数，并根据一些条件进行过滤和连接。具体的查询逻辑如下：

SELECT a.*, b.s_score AS 01_score, c.s_score AS 02_score
FROM student a
JOIN score b ON a.s_id = b.s_id AND b.c_id = '01'
LEFT JOIN score c ON a.s_id = c.s_id AND (c.c_id = '02' OR c.c_id IS NULL)
WHERE b.s_score > c.s_score

这个查询语句的含义是：从学生表（student）中选择所有学生的信息，同时连接分数表（score）中的两个子查询表 b 和 c。连接条件是学生的 ID 和课程的 ID。在表 b 中，只选择课程 ID 为 '01' 的分数记录。在表 c 中，选择课程 ID 为 '02' 或为空（NULL）的分数记录。然后，通过比较表 b 和表 c 中的分数，筛选出满足 b 分数大于 c 分数的记录。

请注意，这只是一个 SQL 查询语句的解释，具体的查询结果取决于数据库中的实际数据。

相关问题

判断下列sql语句的正误select * from student as a inner join score as b on a.s_id=b.s_id inner join score as c on a.s_id=c.s_id and b.c_id=01 and c.c_id=02 where b.s_score>c.s_score；

这是一个错误的 SQL 语句。问题出在 `b.c_id=01` 和 `c.c_id=02` 这两个条件上。在 SQL 中，数字字面值默认被解析为整数，但是以 0 开头的数字会被解析为八进制。因此，`01` 会被解析为八进制数而不是十进制数。如果你想使用十进制数，应该去掉前导的零，即写作 `1` 和 `2`。所以正确的语句应该是：

SELECT * 
FROM student AS a 
INNER JOIN score AS b ON a.s_id = b.s_id 
INNER JOIN score AS c ON a.s_id = c.s_id AND b.c_id = 1 AND c.c_id = 2 
WHERE b.s_score > c.s_score;

select a.s_id ,a.s_name ,count(b.c_id) as sum_course ,sum(b.s_score)as sum_score from student a left join score b on a.s_id=b.s_id GROUP BY a.s_id,a.s_name

Sure! Here is the SQL query to fulfill your request:

SELECT a.s_id, a.s_name, COUNT(b.c_id) AS sum_course, SUM(b.s_score) AS sum_score
FROM student a
LEFT JOIN score b ON a.s_id = b.s_id
GROUP BY a.s_id, a.s_name;

This query will retrieve the student ID (`s_id`), student name (`s_name`), the total number of courses taken by each student (`sum_course`), and the sum of scores obtained by each student (`sum_score`). The `LEFT JOIN` ensures that all students are included in the result, even if they don't have any scores recorded in the `score` table.

Let me know if you need any further assistance!