TSQL / PHP太慢-重写

Question

I have a table called mainevents, and a table called subevents. For each mainevent there are 3 subevents that I want, which match subname='$sub_name' and eventid. When there are a lot of mainevents, the script is too slow. Dragging slow, 10 seconds to load. When I disable subevents loop, the script loads instantly. I think there might be a shorter/faster/easier way of writing the following. Maybe all in one query. I'm not completely sure.

$a=sqlsrv_query($conn, "SELECT
    eventid,status,name, CONVERT(varchar(100),date,107) AS dt 
    FROM dbo.mainevents WHERE 
    ( date >= '$start_date' AND date <= '$stop_date' ) AND disabled='0'
    ORDER BY category asc");
while($e=sqlsrv_fetch_array($a)){
    $b=sqlsrv_query($conn, "SELECT 
        subid, subname FROM dbo.subevents WHERE
        eventid='$e[eventid]' AND subname='$sub_name' ORDER BY subname");
    while($s=sqlsrv_fetch_array($b)){
        //do stuff
    }
}

Answer 1

Why not join the two tables in the first query?

Where there are no sub events though you will need to put in an outer join or you will not get the main event.

Let the SQL server's optimiser decide what needs looping.

The SQL would be something like this:

SELECT m.eventid, m.status, m.name, CONVERT(varchar(100),date,107) AS m.dt, s.subid, s.subname 
FROM dbo.mainevents m, dbo.subevents s
WHERE m.eventId *= s.eventId
AND ( m.date >= '$start_date' AND m.date <= '$stop_date' ) 
AND m.disabled='0'
ORDER BY m.category asc, s.subname asc

I think that is the correct syntax for an outer join in T-SQL, but it is a long while since I did any T-SQL work! :)