Question

I have tables Member and Transaction. Table Member has 2 columns MemberID and MemberName. Table Transaction has 3 columns, MemberID, TransactionDate, and MemberBalance.

The rows in the tables are as shown below:

Table Member:

MemberID           MemberName
=============================
1                  John
2                  Betty
3                  Lisa

Table Transaction:

MemberID        TransactionDate         MemberBalance
=====================================================
1               13-12-2012              200
2               12-12-2012              90
1               10-09-2012              300

I would like to query for MemberID, MemberName and MemberBalance where the TransactionDate is the latest (max) for each MemberID.

My query is like this:

SELECT 
    t.MemberID, m.MemberName , t.MemberBalance
FROM 
    Member AS m 
INNER JOIN 
    Transaction AS t ON m.MemberID = t.MemberID 
WHERE 
    t.TransactionDate IN (SELECT MAX(TransactionDate)
                          FROM Transaction 
                          GROUP BY MemberID)

This query returns:

MemberID           MemberName         MemberBalance
===================================================
1                  John               200
2                  Betty              90

My problem is, I want the query to return:

MemberID           MemberName         MemberBalance
===================================================
1                  John               200
2                  Betty              90
3                  Lisa               NULL

I want the member to be displayed even if its MemberID does not exist in the Transaction table.

How do I do this?

Thank you.

Answer 1

You need to use LEFT JOIN. Also you had an error in your query because if two members had transactions at the same time you can get two rows for both the users.

Try this

SELECT t.MemberID, m.MemberName , t.MemberBalance
FROM Member AS m 
    LEFT JOIN Transaction AS t ON m.MemberID = t.MemberID AND t.TransactionDate=
    ( 
        SELECT MAX(TransactionDate)
        FROM Transaction T2
        WHERE T2.MemberID=t.MemberID
    )