55 lines
1.4 KiB
MySQL
55 lines
1.4 KiB
MySQL
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-- ========================================
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-- 查询编号206学生的班级数据
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-- ========================================
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-- 查询1：查看编号206的所有班级记录
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SELECT
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sc.id,
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sc.student_id,
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sc.class_id,
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c.class_name,
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sc.status,
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sc.join_time,
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sc.create_time
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FROM student_class sc
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LEFT JOIN class c ON sc.class_id = c.id
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WHERE sc.student_id = 206
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ORDER BY sc.join_time DESC, sc.create_time DESC;
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-- 查询2：查看所有status=1（活跃）的班级
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SELECT
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sc.id,
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sc.student_id,
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sc.class_id,
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c.class_name,
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sc.status,
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sc.join_time
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FROM student_class sc
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LEFT JOIN class c ON sc.class_id = c.id
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WHERE sc.student_id = 206 AND sc.status = 1
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ORDER BY sc.join_time DESC, sc.create_time DESC;
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-- 查询3：查看编号206在课程分配表中的数据
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SELECT
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ca.id,
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ca.course_id,
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ca.student_id,
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ca.class_id,
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co.course_name,
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cl.class_name
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FROM course_assignment ca
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LEFT JOIN course co ON ca.course_id = co.id
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LEFT JOIN class cl ON ca.class_id = cl.id
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WHERE ca.student_id = 206
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ORDER BY ca.create_time DESC;
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-- 查询4：查看所有有多个班级的学生
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SELECT
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student_id,
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COUNT(*) as class_count,
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GROUP_CONCAT(CONCAT(class_id, '(', (SELECT class_name FROM class WHERE id = class_id), ')') SEPARATOR ', ') as classes
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FROM student_class
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WHERE status = 1
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GROUP BY student_id
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HAVING COUNT(*) > 1;
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