Question

Possible Duplicate:
Retrieving the latest note (by timestamp) in a single query from a 1:n table

Hi not sure what I should be doing here as never had to make a query like this.

What I need to do is join a table called _notes with _leads,

Each client has a unique ref and they have several notes in the _notes table.

What I want to do is produce a query that will show all the fields in _leads + the latest note from each client.

What I have so far is,

SELECT
_leads.ID,
_leads.Title,
_leads.Firstname,
_leads.Lastname
_notes.Note,
_notes.`Date`
FROM
_leads
Left Join _notes ON _leads.ID = _notes.Lead_ID
GROUP BY _leads.ID

This Only shows me the first note of each client,
is there a way of getting the query to do what I want.

Answer 1

A subquery is my usual solution to this type of difficulty

SELECT
    _leads.ID,
    _leads.Title,
    _leads.Firstname,
    _leads.Lastname,
    n.Note,
    n.`Date`
FROM _leads
LEFT JOIN (
    SELECT 
        _notes.Lead_ID,
        _notes.Note,
        _notes.`Date`
    FROM _notes
    ORDER BY `Date` DESC
) AS n
ON _leads.ID = n.Lead_ID
GROUP BY _leads.id

If your _notes table also has an ID field then the below could be useful also and would be slightly cleaner using a subquery to return the highest ID associated with each lead and then joining _notes in its entirety based on that

 SELECT
    l.ID,
    l.Title,
    l.Firstname,
    l.Lastname,
    _notes.Note,
    _notes.`Date`
FROM (
    SELECT
        _leads.ID,
        _leads.Title,
        _leads.Firstname,
        _leads.Lastname,
        MAX(_notes.ID) AS Note_ID
    FROM _leads
    LEFT JOIN _notes
    ON _notes.Lead_ID = _leads.ID
    GROUP BY _leads.ID
) AS l
LEFT JOIN _notes
ON _notes.ID = l.Note_ID