加入数据库 [英] joining the database

问题描述

我有两个表名student和studentinfo.
在学生表stuid(主键)的学生姓名中.
在studentinfo stuid(外键)本地地址，永久地址等中.
现在我想做的是，当我打算使用gridview时，我想显示
学生信息表中的学生姓名..比怎么办呢?
请回复.....

i have two table names student and studentinfo.
in student table stuid(primary key) studentname.
in studentinfo stuid(foreign key) local address,permenant address etc..
now what i wanted to do is that when i going for using gridview i wanted to display
student name in student info table.. than how can do this??
pls reply.....

推荐答案

您需要使用联接.它们的工作方式如下:

选择学生姓名，[本地地址]，<其他字段=" as =" required =">来自学生内部，在student.stuid = studentinfo.stuid上加入studentinfo

内部联接为您提供两个表中都存在s匹配的记录.如果两个表都可能不匹配，请改用左联接.

当然，如果只有一个学生名映射到每个studentinfo行，那么就需要问一个问题，为什么他们根本不在单独的表中！

You need to use a join. They work like this:

select studentname, [local address], <other fields="" as="" required=""> from student inner join studentinfo on student.stuid = studentinfo.stuid

Inner join gives you records where there is s match in both tables. If there''s a chance of no match in both tables, use a left join instead.

Of course, if there is only ever a single studentname mapped to each studentinfo row, then the question needs to be asked why they are in separate tables at all!!

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