MySql select qualification expiry dates

I have three MySql tables:

Users: UserId, UserName

Tests: TestId, TestName

Passes: PassId, UserId, TestId, DateTaken

I would like to return a table showing dates of the LATEST tests passed by each user, e.g.

|--------|---------|---------|---------|---------|---------|
|User    |Test A   |Test B   |Test C   |Test D   |Test E   |
|--------|---------|---------|---------|---------|---------|
|James   |Null     |6/3/11   |Null     |Null     |4/3/11   |
|Mark    |Null     |1/4/11   |8/5/11   |23/5/10  |Null     |
|--------|---------|---------|---------|---------|---------|

In this example, James has never passed Tests A, C or 开发者_StackOverflow社区D. He may have taken Test B several times, but the latest was on 6/3/11.

I plan to display this data in an ASP.NET GridView. What is the best method for this - can it be done in a SELECT statement? Please help!

Many thanks in advance.

---

select
u.username,
max(case when testid = 1 then datetaken else null end) as A,
max(case when testid = 2 then datetaken else null end) as B,
max(case when testid = 3 then datetaken else null end) as C,
max(case when testid = 4 then datetaken else null end) as D,
max(case when testid = 5 then datetaken else null end) as E
from users as u
left join passes as p on u.userid = p.userid
group by u.userid

---

To achieve this you would need to use subqueries for each test result Try this:

SELECT User,
    (SELECT MAX(DateTaken) FROM Passes p INNER JOIN Tests t ON p.TestId=t.TestId WHERE p.UserId=u.UserId AND TestName='Test A') AS 'Test A',
    (SELECT MAX(DateTaken) FROM Passes p INNER JOIN Tests t ON p.TestId=t.TestId WHERE p.UserId=u.UserId AND TestName='Test B') AS 'Test B',
    (SELECT MAX(DateTaken) FROM Passes p INNER JOIN Tests t ON p.TestId=t.TestId WHERE p.UserId=u.UserId AND TestName='Test C') AS 'Test C',
    (SELECT MAX(DateTaken) FROM Passes p INNER JOIN Tests t ON p.TestId=t.TestId WHERE p.UserId=u.UserId AND TestName='Test D') AS 'Test D',
    (SELECT MAX(DateTaken) FROM Passes p INNER JOIN Tests t ON p.TestId=t.TestId WHERE p.UserId=u.UserId AND TestName='Test E') AS 'Test E'
FROM Users u

---

This is fairly generic solution. MySQL does support everything I wrote, however there may be a MySQL specific solution that may be better.

Select
    UserName,
    Max(TestA) testa,
    Max(TestB) testb,
    Max(TestC) testc,
    Max(TestD) testd,
    Max(TestE) teste
FROM
(



    SELECT
        u.UserName,
        Case When TestName = "Test A" then p.DateTaken END TestA,
        Case When TestName = "Test B" then p.DateTaken END TestB,
        Case When TestName = "Test C" then p.DateTaken END TestC,
        Case When TestName = "Test D" then p.DateTaken END TestD,
        Case When TestName = "Test E" then p.DateTaken END TestE
    FROM
        Users u
        LEFT JOIN tests t
        ON u.UserId = t.userid
        LEFT JOIN (SELECT
                Max(DateTaken) DateTaken,
                userId,
                TestId,
            FROM 
                Passes
            GROUP BY 
                userId,
                TestId) p
        ON t.testId = p.TestId) t
Group BY
    UserName