SELECT s_name,c_id,s_score from student b WHERE b.s_name="tom" LEFT JOIN sc a on a.s_id = b.s_id; 哪里错了

根据你提供的 SQL 查询语句，我注意到你在 WHERE 子句中使用了别名 "b"，但在 LEFT JOIN 子句中没有使用该别名 "b"。这可能导致查询语句中的错误。

正确的查询语句应该是：

SELECT b.s_name, a.c_id, a.s_score
FROM student b
LEFT JOIN sc a ON a.s_id = b.s_id
WHERE b.s_name = "tom";

相关问题

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

你好!根据您的要求，我理解您需要执行一个查询语句，选择学生表中的所有列，并将 b 表中的 s_score 列作为 '01_score'，将 c 表中的 s_score 列作为 '02_score'。查询条件是 b 表中的 s_score 大于 c 表中的 s_score。同时，使用左连接将 c 表与 a 表关联起来，并且 c 表中的 c_id 值为 '02' 或者为 NULL。以下是相应的 SQL 语句：

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

请注意，以上 SQL 语句仅是根据您的问题所提供的信息编写的，如果有其他条件或要求，请提供更详细的信息。

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!