我对SQL很陌生,但我有一个任务,我有三个看起来像这样的表;
哪里有外键链接每个(Classid - > Classid)(CurrenthomeworkID - > homeworkID)
我需要退回作业标题,我该怎么做?
答案 0 :(得分:0)
您可以join将所有三个表放在一起并从中选择其中任何一个:
SELECT u.userid, c.classid, h.homeworkTitle FROM Users AS u
INNER JOIN Classes AS c ON u.ClassID = c.ClassID
LEFT JOIN Homeworks AS h ON c.CurrenthomeworkID = h.homeworkID