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515439429 发表于 2018-10-7 06:59:52

MySQL的开发必会的sql语句

select * from userinfo5,department5　　select * from userinfo5,department5 where userinfo5.part_id = department5.id
　　select * from userinfo5 left join department5 on userinfo5.part_id = department5.id
　　select * from department5 left join userinfo5 on userinfo5.part_id = department5.id
　　# userinfo5左边全部显示
　　# select * from userinfo5 right join department5 on userinfo5.part_id = department5.id
　　# department5右边全部显示
　　select * from userinfo5 innder join department5 on userinfo5.part_id = department5.id
　　将出现null时一行隐藏
　　select * from
　　department5
　　left join userinfo5 on userinfo5.part_id = department5.id
　　left join userinfo6 on userinfo5.part_id = department5.id
　　select
　　score.sid,
　　student.sid
　　from
　　score
　　left join student on score.student_id = student.sid
　　left join course on score.course_id = course.cid

　　left join>　　left join teacher on course.teacher_id=teacher.ti
　　select count(id) from userinfo5;

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