C#MySQL连接3个表
我目前正在使用C#和Mysql(XAMPP)。我有3个表,如下所示:C#MySQL连接3个表,c#,mysql,xampp,C#,Mysql,Xampp,我目前正在使用C#和Mysql(XAMPP)。我有3个表,如下所示: tblILearnQuestion : IlearnQuestionId, Question tblILearnAnswer : ILearnAnswerId, ILearnQuestionId, StudentId, dateSubmited tblILearnMarks : ILearnMarkId, ILearnAnswerId, Comments, mark 我需要一个查询来获得以下数据:question、stu
tblILearnQuestion : IlearnQuestionId, Question
tblILearnAnswer : ILearnAnswerId, ILearnQuestionId, StudentId, dateSubmited
tblILearnMarks : ILearnMarkId, ILearnAnswerId, Comments, mark
我需要一个查询来获得以下数据:question、studentid、mark和comment
。我尝试过这个方法,但不起作用:
SELECT * FROM tblIlearnQuestion
INNER JOIN tblilearnanswer ON
tblilearnquestion.ilearnquestionid = tblilearnanswer.ilearnquestionid
INNER JOIN ilearnmarks ON
tblilearnanswer.ilearnanswerid = tblilearnmarks.ilearnanswerid
它说有些列不存在,我已经检查过了,我确实正确地命名了数据库中的列。第二个联接中的表的名称似乎有误。您写道您的表名是tblILearnMarks,但您在查询中使用了ilearnmarks。如您所见,tbl缺少前缀。第二个联接中的表似乎有错误的名称。您写道您的表名是tblILearnMarks,但您在查询中使用了ilearnmarks。如您所见,tbl前缀丢失。您的语法与连接有点不一致。这应该会把事情理顺:
select *
from tblIlearnQuestion
inner join tblilearnanswer on tblilearnquestion.ilearnquestionid = tblilearnanswer.ilearnquestionid
inner join tblilearnmarks on tblilearnmarks.ilearnanswerid = tblilearnanswer.ilearnanswerid
您的语法与连接有点不一致。这应该会把事情理顺:
select *
from tblIlearnQuestion
inner join tblilearnanswer on tblilearnquestion.ilearnquestionid = tblilearnanswer.ilearnquestionid
inner join tblilearnmarks on tblilearnmarks.ilearnanswerid = tblilearnanswer.ilearnanswerid
可能是第三个表的名称与您之前在问题中所说的不同,但如果不是,则发布准确的错误消息。可能是第三个表的名称与您之前在问题中所说的不同,但如果不是,则发布准确的错误消息。