Java优学网MySQL左连接入门解析：轻松掌握多表查询与MyBatis实战

SELECT 列名 FROM 左表 LEFT JOIN 右表 ON 连接条件;

// MyBatis映射文件中的配置

SELECT s.student_id, s.student_name, c.course_name
FROM students s
LEFT JOIN courses c ON s.student_id = c.student_id

SELECT

s.student_name,
c.course_name, 
t.teacher_name,
d.department_name

FROM students s LEFT JOIN student_courses sc ON s.student_id = sc.student_id LEFT JOIN courses c ON sc.course_id = c.course_id LEFT JOIN teachers t ON c.teacher_id = t.teacher_id LEFT JOIN departments d ON t.department_id = d.department_id WHERE s.enrollment_year = 2023;