如何从另一个表中获得与另一个表中的名称或ID匹配的相同名称或ID

Question

I am using c# and mysql database
I have 2 tables
1st is for info

(Int primary key)          (varchar)             (int)
    Id                       name                 year
   2015                      user1                 1
   2016                      user2                 2

2nd is for accounts

(Int primary key)        (varchar)               (varchar)
Id (username)              name                   password
2015                       user1                    123
2016                       user2                    123

I want to make query that if I would go to make an account with the same id(username) or name after the login then it will show it in datagrid, but I don't know what query I should use.

That means I want to get a result like this for every account which has the same id or name and not show all the data after the login

3rd table showed in datagrid

Id                                  name                 year
2015                                user1                  1

Answer 1

When a user does « login » then its id is available to the application. Just pass this id to a simple SELECT query (seems like you don't even need a JOIN) :

SELECT
    tblstudent.StudentID, 
    tblstudent.Name, 
    tblstudent.YearLevel 
FROM
    tblstudent 
WHERE tblstudent.StudentID = ?

You want to replace the « ? » with the id of the student that just logged in.